use G_OS_WIN32 and G_HAVE_CYGWIN #defines
* app/app_procs.c * app/gdisplay_color.[ch] * app/gdisplay_color_ui.c: make the ui usable * app/gdisplay.c: enable cdisplay support * modules/Makefile.am * modules/cdisplay_gamma.c: moved gamma functionality to separate -Yosh