* expose the XOR function for BRegions (for now called "ExclusiveInclude")

which already existed in the region backend ported from XOrg


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@23394 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/os/interface/Region.h

@@ -66,6 +66,8 @@ class BRegion {
 
 			void				IntersectWith(const BRegion* region);
 
+			void				ExclusiveInclude(const BRegion* region);
+
  private:
 	friend class BDirectWindow;
 	friend class BPrivate::ServerLink;