Move to GPL v3.

We'll be incorporating the Norwegian dictionary which is covered
under GPL3, so that's the reason for the move.
Norwegian support.

The Norwegian dictionary comes from here:

http://www2.scrabbleforbundet.no/?attachment_id=1620

which claims that the words may be used and redistributed under
GPLv3.
A little house-cleaning.  No code changes.
Fix compiler warnings.