[WIP] More mutations

OK, so far the major gain here is the debug menu properly handling
Threshold mutations.  (It doesn't award the Thresholds since it emulates
natural mutation.  You'll need to cross manually, but it's free.)

Added an Ectothermic beyond Cold-Blooded: gives a speed bonus for temps
above 65F.  Should work BUT since based on ambient ATM (before fire,
lava etc.) I've not formally seen it work.

More forthcoming.
Alpha buff

As it was there wasn't much room to gain Prime.  Though that's
understandable (being a pinnacle of human potential isn't easy) there
ought to be some chance.  So I gave it two of Rivet's, moving the total
traits from 9 to 11.
Threshold safety-check

No, you shouldn't be able to lose a Threshold through mutagen
category-enforcement.  Fixed!
Mutagen-addiction, pass 1

This probably needs some tweaking and more thorough testing than I can
give now (I'm looking to have the stuff generally not addictive unless
you're talking a gallon of it).

But the infrastructure's there.
addiction-tweaking

OK, looks like it's working more or less as intended.  Dialed back the
morale bonuses too.
More tweaks

Makes Raptor talons require Raptor serum and cleans up some stuff in the
addiction.
Adds Grazer

Post-Thresh upgrade for Cattle: can eat grass.  Doesn't do much for
nutrition (5 points for removing the grass, 2 points if you're not
hungry or pass your IN check) but means you'll be able to find food and
prepare fields more efficiently.

Fixes a missed tag-change too.
Draft: Infection Resist/Immune

Should work, but Cata fails to load.  Committing to change branches and
test-compile the master branch.
Revert "Draft: Infection Resist/Immune"

This reverts commit f120633d3a9c2287f23882358018cdf60d2db825.
Changes as requested
Insanely ST lockup
Infection-proofing

Glitch-spotting thanks to Voker57.
Adds Cenobite mutation

Not for everyone, but then if you weren't up for a
little...experimentation, you shouldn't have breached THRESH_MEDICAL.
Adds Deadened mutation

Get this one and you'll never feel pain again.

At least from any source of this world.
As requested
Venom-upgrade

Much nastier venom for Arachnids.

If the new effect-handing code was working properly, that is.
Substance-tol & Alcohol-metabolizing

Tolerance is available at chargen and is basically the reverse of
Lightweight.

Troglobites can eventually develop the ability to largely metabolize
alcohol.  Somebody called for Dwarves?
Tweak

Was one thing when it was restricted to alcohol.  Now that it's broader,
yeah, no longer made obsolete by the upgrade so not removed.
Added Prime statboosts

Here's a reason to go Prime: above-average stat set to 15, below-average
stat set to 11.  Post-threshold for Alpha, requires Alpha mutagen, and
branches off of their normal statups.

Sound good?
Lengthens Cenobite branch

Now it's a more proper Cenobite: much less negative effects from pain.
Too bad that they also recover from pain awfully fast ;)