clean up the fdqueue a bit more, by implementing Greg's

clean up the fdqueue a bit more, by implementing Greg's
suggestions to getting rid of redundant variables, as well as
converting the simple ap_queue_full/ap_queue_empty tests into macros.
This also reinstates the "not_full" condition, which turned out to
be useful afterall in cases where we wanted to prevent the listener
thread from accepting further connections until the worker queue has
room for more.

Submitted by:	[Aaron Bannert <aaron@clove.org>]

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@91223 13f79535-47bb-0310-9956-ffa450edef68