Add support for MSVC's __FUNCSIG__

It is very similar to GCC's __PRETTY_FUNCTION__, except it prints the
calling convention.

Reviewers: majnemer

Differential Revision: http://reviews.llvm.org/D3311

llvm-svn: 205780
diff --git a/clang/lib/Parse/ParseTentative.cpp b/clang/lib/Parse/ParseTentative.cpp
index 330e541..71d1961 100644
--- a/clang/lib/Parse/ParseTentative.cpp
+++ b/clang/lib/Parse/ParseTentative.cpp
@@ -936,6 +936,7 @@
   case tok::kw___real:
   case tok::kw___FUNCTION__:
   case tok::kw___FUNCDNAME__:
+  case tok::kw___FUNCSIG__:
   case tok::kw_L__FUNCTION__:
   case tok::kw___PRETTY_FUNCTION__:
   case tok::kw___uuidof: