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.


Update the docs to note that SSL now works with the event MPM as per r1470679.

Submitted by: minfrin
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1515476 13f79535-47bb-0310-9956-ffa450edef68