implement require_program and checks in targets

require_program (and helper package_installed) can be used to ensure
certain binaries exist and let the user know which packages to install
if they don't. Remove local solutions in lgeneral, quake, quake2
and wolf3d.
Small alterations to doom2's LONGNAME
tweak hexen2 LONGNAME
Initial support for Quake2 MP "The Reckoning".
strip game.so binary
the quake2-xatrix .deb is arch-dependent ("any")
q2xatrix: download source by default

Default to downloading the q2xatrix source from a known location
and building it, providing an option for the user to supply a local
copy if they already have it.

TODO: We need to strictly verify sums if we download it, and permit
the user to relax the check if they supply it (or in all cases, not
sure yet)
q2xatrix: verify hash of quake2-xatrix-2.00.tar.xz
q2xatrix: add -f flag to force skip of md5sum check

Allow the user to override the checksum check for quake2-xatrix.tar.xz.

This is useful if a more recent upstream version exists than we know about
and the user is confident that the file they have is legit (or are prepared
to take the risk)
q2xatrix: install upstream LICENSE file

Take opportunity to correct some spelling mistakes too
Small alteration to the q2xatrix LONGNAME
use require_program in q2xatrix for gcc/make/etc.

Use require_program in x2xatrix to make sure we have gcc, make and binutils.
q2xatrix: double-check number of arguments

double-check number of arguments after processing command-line
arguments.
abstract and move stuff from q2xatrix→q2mp-common

…to facilitate implementing q2rogue
initial q2rogue support
tweak control file long description
document recent changes
Merge tag '36' of ssh://anonscm.debian.org/git/pkg-games/game-data-packager

tagging 36
Imported Debian version 37

  * q2rogue, q2xatrix: Correctly remove source tarballs when
    cleaning up.
  * Remove some stray placeholder targets that got into the last
    upload by accident.
  * Upload to unstable.
Merge branch 'jmtd'