contrib: Remove various $FreeBSD$ tags not upstream

Sponsored by: Netflix

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

Create the altix project branch. The altix project will add support
for the SGI Altix 350 to FreeBSD/ia64. The hardware used for porting
is a two-module system, consisting of a base compute module and a
CPU expansion module. SGI's NUMAFlex architecture can be an excellent
platform to test CPU affinity and NUMA-aware features in FreeBSD.

- Import the HEAD csup code which is the basis for the cvsmode work.

Don't import tree.h from the distribution - we have our own one in sys.

Add snmp_ntp/Makefile.in to the exclude list.

Don't extract the .gdbinit file from the distribution.

List some more files to be excluded from the original distribution.

Add an exclusion list that lists all the files from the original
distribution that we don't need.