games/xnethack: fix wrong lua version

The game calls for lua 5.4, so USES=lua:54 when unbundling lua (PR #260224).

While we are at it:

 - turn games/nethack-nox11 into flavor games/nethack@nox11
 - simplify Makefile
 - remove archaic pkg-deinstall.in; it's function is superseeded by
   messages pkg-deinstall(8) prints on its own

PR:		260224
Reported by:	wesley.a.wroten@gmail.com