Fix -Wunused-variable 'FD' by using it instead of ND when they're equal but FD
has a more precise type.

llvm-svn: 200889
diff --git a/clang/lib/AST/MicrosoftMangle.cpp b/clang/lib/AST/MicrosoftMangle.cpp
index 6ce7018..8563f2e 100644
--- a/clang/lib/AST/MicrosoftMangle.cpp
+++ b/clang/lib/AST/MicrosoftMangle.cpp
@@ -1093,11 +1093,11 @@
     if (const FieldDecl *FD = dyn_cast<FieldDecl>(ND)) {
       mangleMemberDataPointer(cast<CXXRecordDecl>(FD->getParent()), FD);
     } else if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND)) {
-      const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(ND);
+      const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD);
       if (MD && MD->isInstance())
         mangleMemberFunctionPointer(MD->getParent(), MD);
       else
-        mangle(ND, "$1?");
+        mangle(FD, "$1?");
     } else {
       mangle(ND, TA.isDeclForReferenceParam() ? "$E?" : "$1?");
     }