No need to re-map the return values of `wp_parse_id_list()` to int. 

See #22074, #11823.



git-svn-id: https://develop.svn.wordpress.org/trunk@25169 602fd350-edb4-49c9-b593-d223f7449a82
Basic tests for wp_parse_id_list() to ensure positive integers. see [25169].



git-svn-id: https://develop.svn.wordpress.org/trunk@25170 602fd350-edb4-49c9-b593-d223f7449a82