nuke unused gdkpixbuf
don't check kernel version when overriding

Always reject OVERRIDE_LINUX_NONBASE_PORTS value based on whether it's
valid not whether compat.linux.osrelease is high enough. The logic for
rejecting unsupported linux kernel is already in bsd.linux-rpm.mk.
linux-c6-curl depends on libldap-2.4.so.2

The check actually causes syntax error if OVERRIDE_LINUX_NONBASE_PORTS
is set to a non-valid value.
import bsd.linux-rpm.mk and bsd.sites.mk
add CentOS 6 support to bsd.*.mk properly
set common defaults
avoid setting values that are already default
add src checksums

This should unbreak PACKAGE_BUILDING builds such as those
done by tinderbox and poudriere.
add libuuid source
Merge pull request #2 from hadvaid/proper

better infra support