Do not throw a TypeError when trying to set global, ignoreCase, source, etc.

regexp_test.go

@@ -199,6 +199,14 @@ func TestRegExp_source(t *testing.T) {
         var def = new RegExp(abc);
         [ abc.source, def.source, abc.source === def.source ];
     `, ".,.,true")
+
+	test(`
+        var abc = /./i;
+        var def = abc.hasOwnProperty("source");
+        var ghi = abc.source;
+        abc.source = "xyzzy";
+        [ def, abc.source ];
+    `, "true,.")
 }
 
 func TestRegExp_newRegExp(t *testing.T) {

type_regexp.go

@@ -306,7 +306,7 @@ func (self *_regExpStash) put(name string, value Value) {
 	switch name {
 	case "global", "ignoreCase", "multiline", "source":
 		// TODO Is this good enough? Check DefineOwnProperty
-		panic(newTypeError())
+		return
 	case "lastIndex":
 		self._regExpObject.LastIndex = value
 		return