Add an example of indirectly modifying readonly property

Author: vrana

language/oop5/properties.xml

@@ -300,6 +300,7 @@ $test->i++;
 ++$test->i;
 $test->ary[] = 1;
 $test->ary[0][] = 1;
+unset($test->ary[0]);
 $ref =& $test->i;
 $test->i =& $ref;
 byRef($test->i);