Support L__FUNCTION__ in microsoft mode, PR11789

Heavily based on a patch from
Aaron Wishnick <aaron.s.wishnick@gmail.com>.

I'll clean up the duplicated function in CodeGen as
a follow-up, later today or tomorrow.

llvm-svn: 159060
diff --git a/clang/lib/Parse/ParseTentative.cpp b/clang/lib/Parse/ParseTentative.cpp
index c2e539c..8a5e7266 100644
--- a/clang/lib/Parse/ParseTentative.cpp
+++ b/clang/lib/Parse/ParseTentative.cpp
@@ -744,6 +744,7 @@
   case tok::kw___imag:
   case tok::kw___real:
   case tok::kw___FUNCTION__:
+  case tok::kw_L__FUNCTION__:
   case tok::kw___PRETTY_FUNCTION__:
   case tok::kw___has_nothrow_assign:
   case tok::kw___has_nothrow_copy: