Meaningful parameters.

[Stanley Sutton]

Since I'm in actions.c, documenting, I'm trying to modify the parameter
names to someting a little easier to follow while I'm changing things.

I'm pretty uniformly changing *unit to *actor, m to material, n to
amount.  After that, things are a bit less uniform.  It's wordier (more
wordy?), but I think it reads a little better.  Of course, it means
backtracking and changing things I've already documented, and changing a
fair amount of code, but it's probably worth the effort.