Gets us compiling again on FreeBSD. Adds conditional compilation around

thread mutex routines for when we don't have APR_HAS_THREADS.

Submitted by:	Justin Erenkrantz
Reviewed by:	Aaron Bannert


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@92061 13f79535-47bb-0310-9956-ffa450edef68