A fits loader for the imlib2 library.

A fits loader for the imlib2 library.

The hardest part was compiling it. I'm using gbilo make file but the
commands on doit.sh also work. This last was what I was able to figure
out from the makefile of the GIF loader. In this first commit, I'm able
to see somekind of image but the rescaling hasn't been done yet. The
fits writer needs to written also (.argb). This loader was started by
editing the loader_argb.c. TODO: make it more robust, better handling of
data types, check if there are datamin datamax values in the header.