Complement to r1542327 (Streamline and improve ephemeral key handling):

the change to acinclude.m4 (part of r1527294) was left out from the
backport proposal by mistake.

Originally proposed by: kbrand. Reviewed by: jim, jorton (cf. r1542297).


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1555469 13f79535-47bb-0310-9956-ffa450edef68