Support conversion from a null pointer constant o any Objective-C object pointer type. Fixes rdar://problem/6463298

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@61340 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/SemaObjCXX/overload.mm b/test/SemaObjCXX/overload.mm
index badba16..397a471 100644
--- a/test/SemaObjCXX/overload.mm
+++ b/test/SemaObjCXX/overload.mm
@@ -76,6 +76,9 @@
   int& i1 = qualid(a);
   int& i2 = qualid(b);
   float& f1 = qualid(c);
+
+  id<P0> p1 = 0;
+  p1 = 0;
 }