import "Fl_GIF_Image" files (renamed to "Fl_Animated_GIF_Image") from KleineBre's FLTK stuff (http://ringbreak.dnd.utwente.nl/~mrjb/fltk/)
build Fl_Animated_GIF_Image class
clean-up Fl_Animated_GIF_Image class; fixed memory leak on class destructor.