introduce REWRITELOG_DISABLED compiler option, which -- if supplied --

strips all logging code from mod_rewrite. This is meant as a performance
improvement for production sites, not as a recommended compiler option
for public distributions.

At least conceptionally this was
Reviewed by:	Justin Erenkrantz, Mads Toftum, Thom May,
		David Burry <dburry@tagnet.org>


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@100904 13f79535-47bb-0310-9956-ffa450edef68