classes: new copy(), copy(w,h), desaturate(), color_average(), and
inactive() methods, alloc_xyz member for copied data, etc.
Updated test programs to use inactive() and copy() methods to create
inactive images for the test buttons, plus the inactive button to toggle
it...
Added start of separate image classes, a la 2.0, for various image formats.
FLUID will also be updated for it...
git-svn-id: file:///fltk/svn/fltk/branches/branch-1.1@1703 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
