When the hero has random clairvoyance, the code used
| (moves % 15) == 0 && rn2(2) != 0
(where 'moves' is actually the turn number) to decide when it would
kick in and show a portion of the map. If the hero was fast enough
to get an extra move when the turn value met the (moves % 15) == 0
condition then clairvoyance could happen twice (or more if poly'd)
on the same turn.
The changes (one new field, reordering a few others) in 'struct
context' invalidate existing 3.7.0-x save files.
Fixes#266
48a82fea8c