Merge r1546759, r1546760 from trunk:

Add suspend_connection and resume_connection hooks to notify modules
when the thread/connection relationship changes.  (Currently implemented
only for the Event MPM; should be implemented for all async MPMs.)


follow-up to r1546759: remove an inadvertently committed testcase
Submitted by: trawick
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1587695 13f79535-47bb-0310-9956-ffa450edef68