Merge r1629925, r1629927, r1629928, r1733162, r1733173 from trunk:

Ensure that httpd exits with an error status when the MPM fails
to run.  [Yann Ylavic]


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1735381 13f79535-47bb-0310-9956-ffa450edef68