Shared fdqueue code between MPMs event and worker into mpm_fdqueue.

This first step moves the files server/mpm/event/fdqueue.[ch] to
server/mpm_fdqueue.[ch] (untouched for now, simple svn move).

Will follow up with the necessary changes to mpm_unix.* for common code.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1821624 13f79535-47bb-0310-9956-ffa450edef68