objc messages have side effects, return true from hasLocalSideEffect,
fixing:

VoidMethod.m:14:5: warning: expression result unused
    [Greeter hello];
    ^~~~~~~~~~~~~~~



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@42380 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/AST/Expr.cpp b/AST/Expr.cpp
index ffd2d3e..0b1c799 100644
--- a/AST/Expr.cpp
+++ b/AST/Expr.cpp
@@ -259,6 +259,8 @@
     // TODO: check attributes for pure/const.   "void foo() { strlen("bar"); }"
     // should warn.
     return true;
+  case ObjCMessageExprClass:
+    return true;
     
   case CastExprClass:
     // If this is a cast to void, check the operand.  Otherwise, the result of