No injecting past non-purifiability

No loophole for you!
Under Construction

FWIW the category-mutagens don't seem to be accepting the dual-prereqs
as easily as the standard ones.  Looking into the matter.
Good to go

Includes some syntax fixes too.  Now to actually get the Threshold
effects together (they'll be one-offs in the iuse, I think.)
Safety-catch

I'll handle the threshold-gaining in a separate PR--it'll likely show up
in the iuse, be a roll that gets easier based on your category strength.
Remove testbed remnant

"MAYBE" was the test trait for prereqs2.  You needed (("CLAWS" ||
"CLAWS_RETRACT") && "PREREQ") to get "MAYBE".

The Threshold trait was UHUH and the test-trait that required it was
NOPE, incidentally.  Dev trivia FTW.
Thresholds and initial post-Thresh mutations

There will be more post-thresh and double-prereqs.  But these ought to
start things off well.
Minor style fixes.
Fix vehicle facing when dragging, thanks to BevapDin for making the same fix in map::rotate().
WIP

Committing to change-branch.  The changes to mutation.cpp are useful,
the rest not yet so much.
new professions and items
added pda
Louisville Slaughterer tweak
tweak burnt out LS's description
grammar and format
Added more girl stuff
format
format, item group
.
tweak
more tweak