Added proc for can_shred() on robots.
Fixed brain transplant issue.
Added xenomorph exclusions to space suits and helmets.
Fixed incorrect role check on leap().
Fixed incorrect cuff resist time when species with can_shred() resisted.
Typo from robotslash commit.
NO_PAIN will now properly stop hard stun from taking effect.
Amending stun commit.

Stun will properly be set to 0 if the species has NO_PAIN.
Merge pull request #7543 from Zuhayr/xenofixes

Xeno fixes.