* Rationalise the two ap_unescape_url versions

* Fix ap_unescape_url_keep2f to work as documented (keep %2F encoded,
  bringing it into line with the documentation as well as common sense).
* Introduce suggestion of an extension to the API
The most relevant open PR is 41798


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@578332 13f79535-47bb-0310-9956-ffa450edef68