Remember to add a has_feature macro for __underlying_type now that it is
correctly impelmented

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@135401 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index ecd4d4c..e865825 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -649,6 +649,7 @@
            .Case("is_trivially_copyable", LangOpts.CPlusPlus)
            .Case("is_union", LangOpts.CPlusPlus)
            .Case("tls", PP.getTargetInfo().isTLSSupported())
+           .Case("underlying_type", LangOpts.CPlusPlus)
            .Default(false);
 }