[Nmh-workers] Improving the format documentation

[Ken Hornstein]

I've just put a small new section in mh-format.5 called "Other Hints and
Tips" to help document some of the oddity surrounding the format syntax.
I had two questions for everyone:

- If you have some free time, would you be willing to take a look at that
  section and give some feedback?

- If you have any other oddities about the format syntax that you think
  should be documented, please speak up!  I'd like to get them in there.

--Ken