Prevent premature macro expansion in __has_builtin, __has_feature,
__has_attribute, __has_extension, making them behave more akin to
conventional macros.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@168268 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index 6baa593..1e77317 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -1228,15 +1228,15 @@
     IdentifierInfo *FeatureII = 0;
 
     // Read the '('.
-    Lex(Tok);
+    LexUnexpandedToken(Tok);
     if (Tok.is(tok::l_paren)) {
       // Read the identifier
-      Lex(Tok);
+      LexUnexpandedToken(Tok);
       if (Tok.is(tok::identifier) || Tok.is(tok::kw_const)) {
         FeatureII = Tok.getIdentifierInfo();
 
         // Read the ')'.
-        Lex(Tok);
+        LexUnexpandedToken(Tok);
         if (Tok.is(tok::r_paren))
           IsValid = true;
       }