* configure.in, acinclude.m4: Substitute AP[RU]_CONFIG with location

of installed ap[ru]-config scripts so third-party modules can use
`apxs -q APR_CONFIG`.

* support/apxs.in: Use new AP[RU]_CONFIG variables; use apr-config
--apr-libtool.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@104641 13f79535-47bb-0310-9956-ffa450edef68