Pain-check

This fixes #7781 by interrupting activities/sleep when you take pain.
Might go better in creature.cpp's mod_pain; I'm not sure if NPCs handle
that yet.
Formula

This ought to cover what we discussed.
No Skating on the Broken Legs

As reported on the forums:
http://smf.cataclysmdda.com/index.php?topic=7248.0

If you're knocked down or are short a leg/two, no skating speed bonus
for you!
Merge remote-tracking branches 'dda/pr/8292' and 'dda/pr/8309' into dda-master

* dda/pr/8292:
  Formula
  Pain-check

* dda/pr/8309:
  No Skating on the Broken Legs
Formatting.