Implement parsing and code generation of Objective-C string literals.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@41238 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Parse/ParseExpr.cpp b/Parse/ParseExpr.cpp
index 75414f7..aa8ced3 100644
--- a/Parse/ParseExpr.cpp
+++ b/Parse/ParseExpr.cpp
@@ -569,6 +569,8 @@
   case tok::kw_reinterpret_cast:
   case tok::kw_static_cast:
     return ParseCXXCasts();
+  case tok::at:
+    return ParseObjCExpression();
   default:
     Diag(Tok, diag::err_expected_expression);
     return ExprResult(true);