Support @compatibility_alias at run time (GNUstep Runtime)

Patch by Niels Grewe!

llvm-svn: 149401
diff --git a/clang/lib/CodeGen/CGObjCRuntime.h b/clang/lib/CodeGen/CGObjCRuntime.h
index 3e0c047..39523c9 100644
--- a/clang/lib/CodeGen/CGObjCRuntime.h
+++ b/clang/lib/CodeGen/CGObjCRuntime.h
@@ -140,6 +140,9 @@
   /// Generate a class structure for this class.
   virtual void GenerateClass(const ObjCImplementationDecl *OID) = 0;
 
+  /// Register an class alias.
+  virtual void RegisterAlias(const ObjCCompatibleAliasDecl *OAD) = 0;
+
   /// Generate an Objective-C message send operation.
   ///
   /// \param Method - The method being called, this may be null if synthesizing