core, mod_ssl: Lift the restriction that prevents mod_ssl taking

full advantage of the event MPM. Enable the ability for a module
to reverse the sense of a poll event from a read to a write or vice
versa.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1470679 13f79535-47bb-0310-9956-ffa450edef68