Update "init_location", etc.

Removed the "get_boosted_stat_value" and "init_location_map" functions
(the latter being absorbed into "init_location"), adjusted the "init",
"deinit", "init_location", "init_player", "init_npc",
"get_nth_item_type", "show_narration", "menu_draw_row_callback", and
"menu_select_callback", functions, and reduced the constant values for
map width/height and MAX_HEAVY_ITEMS.