Merge r1783849 from trunk:

MPMs unix: Place signals handlers and helpers out of DSOs to avoid
a possible crash if a signal is caught during (graceful) restart.
PR 60487.

Reviewedby: ylavic, wrowe, icing


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1797368 13f79535-47bb-0310-9956-ffa450edef68