[Windows] Abstract pure virtual method calls in the ABI. Fix the Windows ABI to forward to the correct function.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@160373 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGCXXABI.h b/lib/CodeGen/CGCXXABI.h
index 4767205..a0dcdfd 100644
--- a/lib/CodeGen/CGCXXABI.h
+++ b/lib/CodeGen/CGCXXABI.h
@@ -193,6 +193,9 @@
   virtual void EmitReturnFromThunk(CodeGenFunction &CGF,
                                    RValue RV, QualType ResultType);
 
+  /// Gets the pure virtual member call function.
+  virtual StringRef GetPureVirtualCallName() = 0;
+
   /**************************** Array cookies ******************************/
 
   /// Returns the extra size required in order to store the array