Improve RegExp.prototype.compile (#2971)

This patch fixes the return value of the routine also fixes several incorrect regression-tests
due to the previously incorrect [[RegExpMatcher]] internal slot check.

JerryScript-DCO-1.0-Signed-off-by: Robert Fancsik frobert@inf.u-szeged.hu

tests/jerry/regression-test-issue-783.js

@@ -12,4 +12,9 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-RegExp.prototype.compile(RegExp.prototype);
+try {
+  RegExp.prototype.compile(RegExp.prototype);
+  assert(false);
+} catch (e) {
+  assert (e instanceof TypeError);
+}