New fbWalkCompositeRegion() function

This new function walks the composite region and calls a rectangle
compositing function on each compositing rectangle. Previously there
were buggy duplicates of this code in fbcompose.c and
miext/rootles/safealpha/safeAlphaPicture.c.

fb/fbpict.h

@@ -630,6 +630,36 @@ fbComposite (CARD8      op,
 	     CARD16     width,
 	     CARD16     height);
 
+typedef void	(*CompositeFunc) (CARD8      op,
+				  PicturePtr pSrc,
+				  PicturePtr pMask,
+				  PicturePtr pDst,
+				  INT16      xSrc,
+				  INT16      ySrc,
+				  INT16      xMask,
+                                  INT16      yMask,
+				  INT16      xDst,
+				  INT16      yDst,
+				  CARD16     width,
+				  CARD16     height);
+
+void
+fbWalkCompositeRegion (CARD8 op,
+		       PicturePtr pSrc,
+		       PicturePtr pMask,
+		       PicturePtr pDst,
+		       INT16 xSrc,
+		       INT16 ySrc,
+		       INT16 xMask,
+		       INT16 yMask,
+		       INT16 xDst,
+		       INT16 yDst,
+		       CARD16 width,
+		       CARD16 height,
+		       Bool srcRepeat,
+		       Bool maskRepeat,
+		       CompositeFunc compositeRect);
+
 /* fbtrap.c */
 
 void