Replace all alarms and timeouts with a mutex on alloc.

Replace file descriptors with APRFile.
Add ap_is_aborted macro.

Submitted by:	Bill Stoddard, Dean Gaudet


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@83766 13f79535-47bb-0310-9956-ffa450edef68