Merge r1821558, r1821561, r1821595 from trunk:

mod_event: Let the listener thread do its maintenance job on resources shortage.

PR 61979.


Follow up to r1821558: CHANGES typo.


mpm_event: Follow up to r1821558.

Don't crash (in listener) if we can't create the ptrans allocator.


Submitted by: ylavic
Reviewed by: ylavic, jim, icing


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1823644 13f79535-47bb-0310-9956-ffa450edef68