Implement EscapeRegExpPattern method (#3543)

the algorithm is based on ECMA-262 v6, 21.2.3.2.4

JerryScript-DCO-1.0-Signed-off-by: Adam Szilagyi aszilagy@inf.u-szeged.hu

tests/jerry/es2015/regexp-prototype-source.js

@@ -0,0 +1,40 @@
+// Copyright JS Foundation and other contributors, http://js.foundation
+//
+// 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 regexp = /fooBar/ig;
+assert(regexp.source === 'fooBar');
+
+assert(new RegExp().source === '(?:)');
+
+assert(new RegExp('/foo/').source === '\\/foo\\/');
+assert(new RegExp('/foo/').source.length === 7);
+
+assert(new RegExp('bar', 'ug').source === 'bar');
+
+assert(new RegExp('/\?/').source === '\\/?\\/');
+assert(new RegExp('/\?/').source.length === 5);
+
+assert(new RegExp('\n').source === '\\n');
+
+assert(new RegExp('\r').source === '\\r');
+
+assert(new RegExp('\u2028').source === '\\u2028');
+
+assert(new RegExp('\u2029').source === '\\u2029');
+
+assert(new RegExp('/\n/').source === '\\/\\n\\/');
+assert(new RegExp('/\n/').source.length === 6);
+
+assert(new RegExp(/\/\//).source === '\\/\\/');
+assert(new RegExp(/\?\//g).source === '\\?\\/');