Bunch of minor fixes for xenomorphs and borer husks.

Implements species default languages (used with 'say' and no language code). Adds Galactic Common and Xenomorph (:0 and :4 respectively).

Fixes the following from #6613:
- Plural issues with eyeballs and kidneys. (the dead eyeballs is dead)
- Husk ichor piles up on the same tile instead of merging with the decal below it.
- Toxin filter has no sprite.
- Missing lungs do nothing, should suffocate the person.
- Missing organs do not show up on the scanner.
- Xenobrain has the regular brain sprite/object, maybe resprite it.
- Dead brains can be placed in an MMI.
- Nutrient vessel has a diona nymph sprite.
- carbon/alien cannot use say emotes.
- Aliens are understood by other humans.
- Xeno language doesn't check for hive node in speaker or receivers when broadcasting.
Interesting. 

So if your lungs are bruised you will be able to breathe normal atmosphere but might have trouble in thin air, (in addition to the occasional punctured lung effect that happens now).

And if your lungs are broken you will not be able to breathe in normal atmosphere without an oxygen mask.