Bcopy, bzero and bcmp on a not-Berkeley machine

[Keith Bostic]

> Where is it guaranteed that bcopy handles overlapping ranges correctly?
> It's not in the BSD 4.3 man page.

This was unfortunate, and has been fixed.  The bcopy instruction was
originally modeled after the VAX MOVC instruction, which is clearly
documented to handle overlap.  Besides, not handling overlap is stupid.

--keith