Eliminated hidden damage factors

Rooting deep, deep into the code, I found that all fire skill based
damage is only 90% effective, and all slash skill based damage is only
80% effective. I believe this is a relic of a stroke system that was
never finished - there is also thrust, which has a low hit factor and a
high damage factor, and unarmed (punch).

In any case, these two hidden factors make it very difficult to balance
weapons. They're in a completely different part of the code, and it
doesn't make sense that slash weapons do less than bows. This might be a
big reason why melee weapons are underpowered - they have been receiving
a hidden 20% damage cut.