Update Clang for 3.5 rebase (r209713).

Change-Id: I8c9133b0f8f776dc915f270b60f94962e771bc83
diff --git a/lib/ARCMigrate/Transforms.h b/lib/ARCMigrate/Transforms.h
index 54be5b5..12551d2 100644
--- a/lib/ARCMigrate/Transforms.h
+++ b/lib/ARCMigrate/Transforms.h
@@ -189,7 +189,7 @@
 
   typedef RecursiveASTVisitor<BodyTransform<BODY_TRANS> > base;
 public:
-  BodyTransform(MigrationPass &pass) : Pass(pass), ParentD(0) { }
+  BodyTransform(MigrationPass &pass) : Pass(pass), ParentD(nullptr) { }
 
   bool TraverseStmt(Stmt *rootS) {
     if (rootS)