Per discussions at https://lists.wisc.edu/read/messages?id=26793770 and https://issues.jasig.org/browse/MAS-75, use flock() instead of apr_file_lock() and apr_file_unlock()
Merge branch 'use-flock' into production
Keep ticket for proxied backend services
Fix infinite redirect loop.

Handle the edge case where gateway-ing is enabled, the upstream CAS
session has expired but the client still sends a MOD_AUTH_CAS cookie.

If we redirect to the CAS server with a query string of
"service=request_uri&gateway=true", we'd create an infinite loop.

See https://issues.jasig.org/browse/MAS-52
added CASValidateRedirectTicket Parameter to allow bypassing the 302 redirect after ticket validation.  This allows CAS enabled web services without the clients required to handle a 302 redirect.
fix README to show CASValidateRedirectTicket in directory/.htaccess settings