Rework the apxs -cp command to work when the source dir isn't available by

querying apr-config and apu-config at link-time instead.

(Note that the $apr_config value in configure.in isn't sufficient as we
need to know where apr-config will be when we execute apxs later on -
hence the --bindir option to apr-config and apu-config.)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@96905 13f79535-47bb-0310-9956-ffa450edef68