Manoj has been pushing for this for a while, but I've been too dense

Manoj has been pushing for this for a while, but I've been too dense
to understand that he was right.  :-)  Basically, this makes the modules
use ap_config to test for header file inclusion.  This method is not to
be used for larger modules that run autoconf theirselves.  Including
ap_config is only valid for modules which rely on Apache to do their
configuration.  Currently, this is only the core modules.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@84497 13f79535-47bb-0310-9956-ffa450edef68