Fix a bunch of cases where the return code of the regex compiler

was not checked properly. This affects: mod_setenvif, mod_usertrack,
mod_proxy, mod_proxy_ftp and core.

PR: 28218
Reviewed by: Jeff Trawick, Joe Orton


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@103823 13f79535-47bb-0310-9956-ffa450edef68