spell skils for role-specific special spell

spell skils for role-specific special spell

Every role has a specific spell that they having an easier time
casting.  Samurai's special spell is clairvoyance but samurai is
restricted in divination spells.  Requested about 4.5 years ago:
allow samurai to achieve basic skill in divination.

Similar for barbarian, special spell is haste self but escape spells
are restricted.  All the other roles can already get at least basic
in their special spell's category.

There were several choices:
1) leave things as they are;
2) give those two roles different special spells;
3) allow them to reach basic in the spell category of the existing
   special spell;
4) #2 for one of those roles, #3 for the other.

I went with #3.  To compensate, reduce attack spell skill limit from
skilled to basic for both.  (#4 might be better, since the reason to
want divination enhanced is most likely identify and magic mapping,
not interest in clairvoyance.)