add test_stability.sh script to test last N commit for perf

benchmarks/jerry/loop_arithmetics_1kk.js

@@ -0,0 +1,30 @@
+// Copyright 2014 Samsung Electronics Co., Ltd.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+var count = 1000000;
+var x = 7;
+var y = 3;
+
+var tmp1;
+var tmp2;
+var tmp3;
+var tmp4;
+
+for (var i = 0; i < count; i++)
+{
+  tmp1 = x * x;
+  tmp2 = y * y;
+  tmp3 = tmp1 * tmp1;
+  tmp4 = tmp2 * tmp2;
+}