Rename HAVE_SYSTEMD conditional into WANT_SYSTEMD
Use HAVE_SYSTEMD macro definition instead of WANT_SYSTEMD
Set udevrulesdir only for platforms with udev
The activation method on OS X is "manual" as we do not offer launchd support
Make sure configuration summary outputs correctly on OS X
Only conditionally compile bits of udev and systemd support
Add a pkg-config requirement check in autogen.sh
Bump autoconf requirement to 2.64
Set bug report and home page URLs in AC_INIT()