Weakening/doc

• Weakening is a mutation that infrequently increases your pain stat by 1 while causing minor damage. While it is only a minor nuisance, this mutation can potentially downgrade further into Disintegration if you're not too careful, or are particularly unlucky. Unfortunately, the pain caused by weakening is insufficient to trigger masochism, and so cannot be relied upon to gain a permanent morale boost by this such a method.