USE_PTHREAD_SERIALIZED_ACCEPT on AIX 4.3. This provides a substantial

performance improvement on multi-CPU machines serving large numbers of
clients.

Submitted by:	Victor Orlikowski
Reviewed by:	Bill Stoddard


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@85480 13f79535-47bb-0310-9956-ffa450edef68