AIX: Change the default accept mechanism from pthread back to

AIX: Change the default accept mechanism from pthread back to
fcntl.  Idle child cleanup doesn't work when the child selected
for termination by the parent is waiting on a pthread mutex, and
because the AIX kernel's notion of hot process is apparently the
same as Apache's, it is common for the Apache parent to continually
select a child for termination that the kernel will leave waiting
on the mutex for extended periods of time.  There are other
concerns with pthread mutexes as well, such as the ability to
deadlock the server if a child process segfaults while holding the
mutex.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@99718 13f79535-47bb-0310-9956-ffa450edef68