Compatibility with both Apache 2.2 and 2.4.

The ap_log_rerror function has changed the parameters that it accepts between
Apache 2.2 and 2.4.  The gss_log function wraps around ap_log_rerror, so it
needs to deal with the new parameter that was added.
Merge branch 'gssweb-apache' of ssh://moonshot.suchdamage.org/srv/git/mod_auth_kerb into gssweb-apache