Merge r1825147 from trunk:

* modules/lua/config.m4: Use liblua paths from pkg-config if
  available.

Reviewed by: wrowe, ylavic, jorton


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1825631 13f79535-47bb-0310-9956-ffa450edef68