Backport two small htcacheclean fixes from trunk to the 2.2.x branch;

    1.) Open the cache files as binary types, so that htcacheclean can
        work properly on Windows.

    2.) Add an entry in support/README for htcacheclean



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@289977 13f79535-47bb-0310-9956-ffa450edef68