xgl:  Add fast clear APIs

Added new APIs for optimized clears of color and depth buffers.
Bug# 13172, due to a bug in rev39, this also accounts for the change
in rev41.
diff --git a/xgl.py b/xgl.py
index 225610b..d072877 100644
--- a/xgl.py
+++ b/xgl.py
@@ -436,6 +436,14 @@
              Param("const XGL_IMAGE_CREATE_INFO*", "pCreateInfo"),
              Param("XGL_IMAGE*", "pImage")]),
 
+        Proto("XGL_RESULT", "SetFastClearColor",
+            [Param("XGL_IMAGE", "pImage"),
+             Param("const XGL_FLOAT[4]", "color")]),
+
+        Proto("XGL_RESULT", "SetFastClearDepth",
+            [Param("XGL_IMAGE", "pImage"),
+             Param("XGL_FLOAT", "depth")]),
+
         Proto("XGL_RESULT", "GetImageSubresourceInfo",
             [Param("XGL_IMAGE", "image"),
              Param("const XGL_IMAGE_SUBRESOURCE*", "pSubresource"),