Add support for '__is_literal_type' spelling of the existing
'__is_literal' type trait for GCC compatibility. At least one relased
version if libstdc++ uses this name for the trait despite it not being
documented anywhere.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@130078 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Parse/ParseExpr.cpp b/lib/Parse/ParseExpr.cpp
index d218c79..0ad153f 100644
--- a/lib/Parse/ParseExpr.cpp
+++ b/lib/Parse/ParseExpr.cpp
@@ -989,6 +989,7 @@
   case tok::kw___is_empty:
   case tok::kw___is_enum:
   case tok::kw___is_literal:
+  case tok::kw___is_literal_type:
   case tok::kw___is_pod:
   case tok::kw___is_polymorphic:
   case tok::kw___is_trivial: