Swift SIL: add bridging for witness and default witness tables

include/swift/SIL/SILWitnessTable.h

@@ -223,6 +223,8 @@ public:
                                  RootProtocolConformance *conformance);
 
   ~SILWitnessTable();
+  
+  SILModule &getModule() const { return Mod; }
 
   /// Return the AST ProtocolConformance this witness table represents.
   RootProtocolConformance *getConformance() const {