Backoff aplog_error() to be configureable on a per-server basis.

Attempt to fix portability issues with syslog().
Convert existing log functions to wrappers for aplog_error().
Add #ifdef USE_SYSLOG


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@79093 13f79535-47bb-0310-9956-ffa450edef68