Cleanups from James H: a few missing statics, a precautionary cast

Cleanups from James H: a few missing statics, a precautionary cast
or two, a debugging fix, a couple of explicit initialisations of
variables that were previously read uninitialised, and a fix for a
whopping great big memory leak in Slant owing to me having
completely forgotten to write free_game().

[originally from svn r6159]