merge from trunk:

  Worker MPM: On graceless shutdown or restart, send signals to
  each worker thread to wake them up if they're polling on a
  Keep-Alive connection.  PR 38737.  [Chris Darroch]

PR: 38737
Reviewed by: chrisd, trawick, niq



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@424876 13f79535-47bb-0310-9956-ffa450edef68