Add "mod_macro" as a standard module, compiled in with "most".

This module was created in 1998 and has been distributed independently
ever since. It is hereby donated to the Apache Software Foundation.

There are quite a few comments in the source code to explain how it works,
as well as extensive non regression tests.

Some utilities about array processing could be moved to "core.c".
However, I finally decided against for now so that it stays as an external
and independent module, and thus may be backported with minimal impact
on the source tree.

Details of the addition:

* modules/core/mod_macro.c: module source code
* modules/core/test: non regression tests
  modules/core/test/conf/: configuration files
  modules/core/test/ref/: expected results
* docs/manual/mod/mod_macro.xml: English documentation
* docs/manual/mod/mod_macro.xml.fr: French documentation



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1435811 13f79535-47bb-0310-9956-ffa450edef68