Get mod_userdir compiling on FreeBSD when APR_HAS_THREADS.

This doesn't account for the fact that getpwnam() isn't
thread-safe on FreeBSD; it also doesn't account for systems
where getpwnam_r lives outside of libc.

See thread with subject "[?PATCH?] using getpwnam_r in mod_userdir"
in Nov. 2000 new-httpd for some better long-term ideas for how to
handle the problem.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@86917 13f79535-47bb-0310-9956-ffa450edef68