[PATCH] Downgrade the error about nested name specifiers when building with Microsoft extensions

[Reid Kleckner]

I'd echo what David said, but otherwise, this seems fine.

================
Comment at: lib/Sema/SemaDecl.cpp:3290
@@ +3289,3 @@
+    Diag(SS.getBeginLoc(),
+         getLangOpts().MicrosoftExt ?
+           diag::ext_standalone_class_nested_name_specifier :
----------------
We use LangOpts.MSVCCompat to control these language bending extensions.

http://reviews.llvm.org/D4333