Fix some aspects of armor absorption.

Fixes a few things that were brought up in #4901:

* Fixes bashing damage being used to calculate cutting damage that bypasses armor. This effectively prevented armor from being damaged by cutting attacks.
* Fixes armor absorption counting twice for the purposes of protecting from damage. Effectively, armor with 8 cut protection would need to take 18 or more points of cutting damage to risk being damaged, now it is correctly 10.