#3 GNUmakefile missing libs error

[Howard Pepper]

When building on 64-bit Linux I received errors telling me that libfltk_jpeg, libfltk_png and libfltk_z were not found. Upon closer inspection, I found out that with the release of fltk 1.1.10, these individual libs had been rolled into libfltk and libfltk_images. This patch simply removes the libfltk_jpeg, libfltk_png and libfltk_z entries from the LIBFILES variable in the GNUmakefile file.

[Howard Pepper]

Patch to remove individual libfltk_jpeg, libfltk_png and libfltk_z entries