randr: Improve per-crtc gamma support.

- The Gamma values from the monitor section are now used during initial config.
- The old colormap system is disabled when gamma set hook is available.
- Gamma values are now persistent for the lifetime of the xserver.
- This requires no driver changes and should be driver ABI compatible.

hw/xfree86/common/xf86cmap.c

@@ -49,6 +49,7 @@
 #include "xf86_OSproc.h"
 #include "xf86str.h"
 #include "micmap.h"
+#include "xf86Crtc.h"
 
 #ifdef XFreeXDGA
 #define _XF86DGA_SERVER_
@@ -141,6 +142,10 @@ Bool xf86HandleColormaps(
     int *indices; 
     int elements;
 
+    /* If we support a better colormap system, then pretend we succeeded. */
+    if (xf86_crtc_supports_gamma(pScrn))
+	return TRUE;
+
     if(!maxColors || !sigRGBbits || !loadPalette)
 	return FALSE;