build apache module mod_gearbox

I had to update mod_gearbox.cc to undefine some PACKAGE_*
that conflicted.  It looks like this is caused by apache's
ap_config_auto.h and gearbox's config.h both defining them

I imported m4/ax_with_apxs.m4 that I found from
https://github.com/timfel/mod_auth_openid/ that looks to be
originally copied from modpython's source.

I'm not sure if I need the apr-1-config stuff.  It may be
unnecessary.