Mass rename C1x references to C11. The name hasn't proliferated like "C++0x" so this patch is surprisingly small.

Also drop -Wc1x-extensions in favor of -Wc11-extensions. I don't think we need to keep this around for compatibility.

llvm-svn: 147221
diff --git a/clang/lib/Parse/ParseTentative.cpp b/clang/lib/Parse/ParseTentative.cpp
index 2c90183..fe46456 100644
--- a/clang/lib/Parse/ParseTentative.cpp
+++ b/clang/lib/Parse/ParseTentative.cpp
@@ -1046,7 +1046,7 @@
   case tok::kw___underlying_type:
     return TPResult::True();
 
-  // C1x _Atomic
+  // C11 _Atomic
   case tok::kw__Atomic:
     return TPResult::True();