Remove penalty for not guessing obscure words.

The list of obscure words is in obscure.txt. It consists of words
that are also in words.txt, but for which blanks lines will not
appear on the game board. If an obscure word is guessed, it will
still be considered valid---a new space for it will be inserted
into the game board and the word will be displayed in green.

Many thanks to Kevin Atkinson and Alan Beale for providing the
2of12inf.txt list from which an attempt at identifying 'obscure'
words in OWL2+LWL could be identified. The 2of12inf.tx list was
obtained from:

	http://wordlist.sourceforge.net/12dicts-readme.html

and details on its copyright and license status are included in
COPYING-wordlists.