Added a new attribute, objc_root_class, which informs the compiler when a root class is intentionally declared.
The warning this inhibits, -Wobjc-root-class, is opt-in for now. However, all clang unit tests that would trigger
the warning have been updated to use -Wno-objc-root-class. <rdar://problem/7446698>

llvm-svn: 154187
diff --git a/clang/test/SemaObjCXX/ivar-construct.mm b/clang/test/SemaObjCXX/ivar-construct.mm
index da066e9..535d2a02 100644
--- a/clang/test/SemaObjCXX/ivar-construct.mm
+++ b/clang/test/SemaObjCXX/ivar-construct.mm
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -fsyntax-only -verify %s
+// RUN: %clang_cc1 -fsyntax-only -verify -Wno-objc-root-class %s
 struct Y { 
   Y();