The present invention refers to a multifunction detaching device for magnetic anti-theft devices. The main commercially available magnetic anti-theft mechanisms are composed, in particular, but not in a limiting way, of anti- theft cases adapted to contain therein and to protect objects such", as, but not limited to, compact discs, DVD, musicassettes, videocassettes and the like, or of elongated anti-theft elements for eyeglasses, or of elements to be attached to garments and the like. Anti-theft mechanisms of this type are known in the art for years; in order to remove the objects contained therein, the ones operating with the magnetic attraction principle must be equipped with so-called "detaching devices" containing magnetic elements with various shapes and sizes: when the anti-theft mechanism is approached to such detaching devices, they magnetically attract the closing elements with which such anti-theft mechanisms are equipped and they allow opening these latter ones and extracting the object contained and protected therein. These opening operations usually occur near the payment counters of commercial shops that are equipped with such anti-theft arrangements and, in the currently marketed versions, these detaching devices have two main types of problems: - due to the presence of magnetic anti-theft mechanisms with various shapes, sizes, and closing and opening methods, it is not rare that, above all in big supermarkets, it is necessary to procure several detaching devices, each one adapted to open a particular type of anti-theft mechanism. This has obvious operating and space problems for responsible operators; - since the detaching devices are usually secured to the surfaces on which they have to operate, they remain, at certain times of the day (for example during the night or on holidays when the commercial shops are closed) , not attended by any operator and therefore they are subjected to be used incorrectly by anyone having access thereto, obviously in order to open the magnetic anti-theft mechanisms and to illegally get their contents. Object of the present invention is solving the above prior-art problems, by providing a multifunction detaching device that allows opening a plurality of different types of magnetic anti-theft mechanisms with a single practical arrangement, with small sizes and composed of very few parts, which allows highly reducing its cost and making its application easier even in restricted areas. A further object of the present invention is providing a multifunction detaching device of the above-mentioned type that is further equipped with means preventing the undesired access to the detaching elements contained therein. The above and other objects and advantages of the invention, as will result from the following description, are obtained by a multifunction detaching device according to Claim 1. Preferred embodiments of the present invention are claimed in the dependent claims . The present invention will be better described by some preferred embodiments thereof, provided as a non-limiting example, with reference to the enclosed drawings, in which: - Figure 1 is a perspective view of the multifunction detaching device of the present invention in its closing position; - Figure 2 is a similar view to Fig. 1 in which the device is shown in its operating opening position; - Figure 3 is a side sectional view of the device of Fig. 1, that shows its components during the closing step; and - Figure 4 is an exploded perspective view of the main components that compose the detaching device of the invention. With reference to the Figures, a preferred, but not limiting, embodiment of the multifunction detaching device 1 of the present invention is shown. It will be immediately- obvious to the skilled people in the art that numerous modifications and variations couLd be performed to the described device 1, without departing from the scope of the invention, as defined in the enclosed claims. With reference to the preferred embodiment shown in the Figures, the multifunction detaching device 1 for magnetic anti-theft mechanisms of the invention substantially comprises: a support body 2; at least one first magnetic detaching element 3 with an elongated shape; and at least one second magnetic detaching element 5 with a circular shape. In particular, the first and second magnetic detaching elements 3, 5 can be placed in a respectively coaxial position, in order to detach a magnetic anti-theft mechanism (for example an anti-theft case) that is equipped with blocking elements both of the lamellar spring type, and of the cylindrical pin-spring type. With this arrangements, the detaching device 1 moreover can be used both for opening common anti-theft cases for compact discs, DVD, musicassettes, videocassettes, eyeglasses and the like, that need elongated detaching elements 3, and for opening anti-theft elements contained, for example, on garments, or on other types of anti-theft cases, that need detaching elements 5 with a circular shape. The detaching device 1, in its preferred embodiment adapted to prevent its illegal use, can be further equipped with anti—theft covering means 7 adapted to prevent an undesired access to the first and second magnetic detaching elements 3, 5. In particular, the anti-theft covering means 7 can be of the detachable type (as shown in. the Figures) from the multifunction detaching device 1 upon their removal when it d_s necessary to activate the multifunction detaching device L, or, according to a not-shown alternative, the anti-theft covering means 7 can be realised integrally with the irvultifunction detaching device 1, and are adapted to be Lifted away from and to allow accessing to the device 1 when -Lt is necessary to activate it, but remain hinged thereto also during the opening step. Moreover, the anti-theft covering means 7 are equipped with blocking means 9 and are adapted to be placed above the multifunction detaching device 1 in order to cover the first and second magnetic detaching elements 3, 5. The blocking means 9 are composed of a latch element 11 and of a key 13 for its actuation between an opening position and a closing position of the anti-theft covering means 7. The latch element 11 is composed of a small elongated cylinder 14 equipped with a projecting tooth 15 adapted to eng-age a corresponding recess 16 obtained in the support body 2 to guarantee the closure of the anti-theft covering means 7 over the multifunction detaching device 1. According to the embodiment shown, the first magnetic detaching element 3 is composed of two elongated parrallelepiped-shape bars 18, 20 placed mutually paired and supported by a bearing element 21, preferably with a circular shape. Also the second magnetic detaching element 5 is supported by a bearing element 23, also preferably of a cirrcular shape. In order to facilitate the detaching operations of the magnetic anti-theft mechanisms, the multifunction detaching device 1 further comprises first alignment means 22 that cooperate with the first magnetic detaching element 3 in order to align the area of the magnetic anti-theft mechanism to be subjected to detachment with the first magnetic detaching element 3. In particular, the first alignment means 22 are composed of an elongated projection arranged in parallel with the first magnetic detaching element 3. The multifunction detaching device 1 further comprises second alignment means 24 that also cooperate with the first magnetic detaching element 3 in order to align the area of the magnetic anti-theft mechanism to be subjected to detachmen-t with the first magnetic detaching element 3. In particular, the second alignment means 24 are composed of a small cylinder 26 and of a spring 28, both placed in the support body 2: the small cylinder 26 cooperates with the spring 28 that keeps the small cylinder 26 projecting outside the support body 2 to guarantee the abutment of a magnetic anti-theft mechanism to be detached on the ffirst magnetic detaching element 3; due to its arrangement, moreover, the small cylinder 26, according to applications, is adapted to be pushed inside the support body 2 if it is not necessary that it projects from the support body 2 to guarantee an alignment. Finally, the support body 2 is equipped with at least one through-hole 30 adapted to allow securing the support body 2 to a surface (not shown) that must be unmovably equipped ^ith the multifunction detaching device 1 of the invention- As regards the materials of which they are composed, the first and second magnetic detaching elements 3, 5 are made of magnetic material, while all other components of the multifunction detaching device 1 are made of light-weight metal (sc-irew, small cylinder, spring) or plastic material, in order to guarantee lightness, compactness and capability to be handled.