Rearrangement and cleanup

Rearrangement and cleanup

* MANIFEST, Makefile: Add coord.cc, poke dependencies
* coord.cc: New file to house coordinate/offset constants.
* default.permons: Set power values for new demons
* map.cc: Clean up stale code accessing stale members of Level
* map.hh: Prune stale members from Level; add Doxygen comments
* permon.hh, permobj.hh: De-confusing sloccount
* rng.cc: Relocate random_step() from main.cc
* u.cc: Relocate do_player_action() from main.cc
* victrix-abyssi.hh: Relocate save_game() prototype from main.cc