Install update-game-score only on request

Install update-game-score only on request

Most distributions do not install update-game-score properly
due to setuid/setgid complications, so install it only when
the installer specifies a user or group (Bug#25895).
* .gitattributes: Remove lib-src/update-game-score.exe.manifest.
* Makefile.in (gameuser, gamegroup, use_gamedir, PATH_GAME):
New vars.
(epaths-force): Use PATH_GAME.
(uninstall): Remove snake-scores and tetris-scores only if shared.
* configure.ac: Default --with-gameuser to 'no'.
(UPDATE_MANIFEST): Remove.
* etc/NEWS: Mention this.
* lib-src/Makefile.in (UPDATE_MANIFEST): Remove.
(use_gamedir): New macro.
(UTILITIES): Remove update-game-score unless use_gamedir.
(SCRIPTS): Remove $(UPDATE_MANIFEST).
($(DESTDIR)${archlibdir}): Install game directory program and data
only if use_gamedir.
* lib-src/update-game-score.exe.manifest: Remove, as
update-game-score is no longer installed on MS-Windows.
* lisp/play/gamegrid.el (gamegrid-add-score-with-update-game-score):
Use auxiliary program only if setuid or setgid.
* make-dist: Do not distribute update-game-score.exe.manifest.
* src/callproc.c (init_callproc):
Set Vshared_game_score_directory based on PATH_GAME, not DOS_NT.
(syms_of_callproc): Remove unnecessary initialization of
Vshared_game_score_directory.