If one fights against a number of bots of a particular bot type, e.g. Acolytes,
Tux is less effective once he advances his hacking program.

E.g.:
At the beginning, Tux has max_temperature 100 and he needs 20 heat for
Hacking-program revision 1.
Therefore, he can takeover 5 Acolytes.

If Tux learns Hacking revision 2, every hacking attempt produces 30 heat.
Now, he can takeover only 3 Acolytes.

It is counter-intuitive that Tux loses the capability of winning against small
bots when he "improves" his hacking program.

This problem can be solved by considering the number of unused charges and the
number of captured rows that would not be neccessary for a win.

In fact, it was pretty easy to implement:
http://rb.freedroid.org/r/1648/

In case of a draw, the full heat will be produced, but if Tux wins his first
attempt and don't use all his charges or wins with more than 7 captured rows, he
produce only the heat of the charges he really needed.

Patch committed in r5362. Thanks!