7171890: C1: add Class.isInstance intrinsic

Class.cast which calls Class.isInstance is heavily used by the new JSR 292 implementation

Reviewed-by: roland

hotspot/src/share/vm/c1/c1_GraphBuilder.cpp

@@ -3170,6 +3170,7 @@ bool GraphBuilder::try_inline_intrinsics(ciMethod* callee) {
       break;
 
     case vmIntrinsics::_getClass      :
+    case vmIntrinsics::_isInstance    :
       if (!InlineClassNatives) return false;
       preserves_state = true;
       break;