Fully convert worker's fdqueue to the new APR lock API:

- Mutexes and Condition Variables from APR are now used instead of
  direct (non-portable) calls to pthread.

Still need to fully APRize these routines, particularly the return
values. In many cases a failed lock or cond var call will simply return
FD_QUEUE_FAILURE. This should obviously instead return the appropriate
APR error code.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@91531 13f79535-47bb-0310-9956-ffa450edef68