Refactor RegExp builtin (#3136)

JerryScript-DCO-1.0-Signed-off-by: Dániel Bátyai dbatyai@inf.u-szeged.hu

tests/jerry/regexp-assertions.js

@@ -167,9 +167,3 @@ t.lastIndex = "2"
 var result = t.exec("abc   abc");
 assert(result[0] === "abc");
 assert(result.index === 6);
-
-t = new RegExp ("abc","g");
-t.lastIndex = -12;
-result = t.exec("abc   abc");
-assert(!result);
-assert(t.lastIndex === 0);