the return value rather than in *error. In the old days type-
checking would have caught this, but now of course they're the same
type.
[originally from svn r6161]
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]
nikoli.co.jp (which has quite a few puzzles that they don't seem to
have bothered to translate into English).
Minor structural change: the disjoint set forest code used in the
Net solver has come in handy again, so I've moved it out into its
own module dsf.c.
[originally from svn r6155]
