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

libgimpwidgets/gimpfileentry.c

@@ -38,7 +38,7 @@
 #include "pixmaps/yes.xpm"
 #include "pixmaps/no.xpm"
 
-#ifdef NATIVE_WIN32
+#ifdef G_OS_WIN32
 # ifndef S_ISDIR
 #  define S_ISDIR(m) ((m) & _S_IFDIR)
 # endif

libgimpwidgets/gimpfileselection.c

@@ -38,7 +38,7 @@
 #include "pixmaps/yes.xpm"
 #include "pixmaps/no.xpm"
 
-#ifdef NATIVE_WIN32
+#ifdef G_OS_WIN32
 # ifndef S_ISDIR
 #  define S_ISDIR(m) ((m) & _S_IFDIR)
 # endif