Refactoring -- moved 3 globals to new struct settings_t

Closed username-removed-1096594 requested to merge traas/open-adventure:master into master

Since logfp, oldstyle, and prompt were application settings, rather than have them all as global vars, move them to a single global var, seperate from game state, as they aren't, technically, game state, but are application settings.

Also enhanced cheat.c