Using a local __choice like in map to avoid unnecessary inconstantness
This is same-behavior, but I would be in favor of reseeding only at the beginning of the day/night instead of every time the summon menu is opened (next commit)
big work
what was reliable before is now not, in recent versions of renpy, which is why we added that new config (which I put in say.rpy, but it can be moved somewhere else)
Also fixes the game_menu's title position, incidentally
some changes are incompatible with my diary and achievement branches, respectively, they will need to be merged with a bit of manual care
- don't use a reserved name (starting with an underscore)
- use a file-local mangled name (starting with two underscores
- use renpy.dynamx to cleanup the variable automatically
