Merge r1530793 from trunk:

core: Don't truncate output when sending is interrupted by a signal,
      such as from an exiting CGI process.

PR: 55643

Submitted by: trawick
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1530999 13f79535-47bb-0310-9956-ffa450edef68