The series of "species nuking" prs made it so that the `fixed_mut_color`
also applies to hair. The problem with that is you may not want that in
some cases. It also introduced a bug where that var prevents ethereals'
hair from changing colors when they die.
So I have moved hair out of the things that gets `FIXED_MUT_COLOR` trait
applied to it in favor of its own thing.
`FIXED_HAIR_COLOR` trait is now used for ethereals to get a fixed hair
color.
Ethereals' hair should go out now when they die again, and it comes back on when they are revived.
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