o Fix proto type

o Fix proto type
o Mention that the left-hand side of the comparison conditional
  must always be a variable expansion.  Do not lie that
  debugging .for loops is a no-op.
o Update tutorial.
o Update man page.
o Fixed the abuses of .Ql visible on stderr in troff mode.
o Fix typos, mostly s/ an / a / where appropriate and a few s/an/and/
  Add FreeBSD Id tag where missing.

Submitted-by: Max Okumoto <okumoto@ucsd.edu>
Taken-from: FreeBSD