fix gangcount updating

The problem was that gangcount was updated from p for only the first
7 elements (0 through 6), leaving element 7 unchanged. This left
garbage in `gangcount[7]` on some machines, and limited the size
of storable numbers to 14 bytes instead of 16.
New CPAN release of Algorithm-AM - v2.44

    Fix gangcount updating (2.42 was correct)