source files from Mike rather than patches, and not adequately
checking the result...
[originally from svn r6882]
[r6780 == f05c25347d66821d928668a7e87dffbf3ffed027]
[r6880 == b9547673c6462bf73e642328300479df6df71d7b]
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]
