* Function : gif_deanimate
*
* Description : Deanimate a given GIF image, i.e. given a GIF with
* an (optional) image block and an arbitrary number
* of image extension blocks, produce an output GIF with
* only one image block that contains the last image
* Function : gif_deanimate
*
* Description : Deanimate a given GIF image, i.e. given a GIF with
* an (optional) image block and an arbitrary number
* of image extension blocks, produce an output GIF with
* only one image block that contains the last image