I've had two complaints that Solo ought to recognise the numeric

I've had two complaints that Solo ought to recognise the numeric
keypad. The reason it doesn't is because front ends were carefully
translating the numeric keypad into 8-way directional keys for the
benefit of Cube. Therefore, a policy change:
 - front ends process the numeric keypad by sending MOD_NUM_KEYPAD |
   '3' and similar
 - front ends running on a platform with Num Lock SHOULD do this
   _irrespective_ of the state of Num Lock
 - back ends do whatever they see fit with numeric keypad keys.
Result: the numeric keypad now works in Solo, and also works in OS X
Cube (which it previously didn't because I forgot to implement that
bit of the front end!).

git-svn-id: svn://svn.tartarus.org/sgt/puzzles@5774 cda61777-01e9-0310-a592-d414129be87e