restore ABI break in r1082630, changed signature of ap_unescape_url_keep2f().

Reviewed By: covener, wrowe, trawick
  http://mail-archives.apache.org/mod_mbox/httpd-dev/201105.mbox/%3C4DD4032F.1070400@p6m7g8.com%3E



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@1124515 13f79535-47bb-0310-9956-ffa450edef68