Headers
-------

   Gnus uses internally a format for storing article headers that
corresponds to the NOV format in a mysterious fashion.  One could
almost suspect that the author looked at the NOV specification and just
shamelessly *stole* the entire thing, and one would be right.

   "Header" is a severely overloaded term.  "Header" is used in RFC1036
to talk about lines in the head of an article (eg., `From').  It is
used by many people as a synonym for "head"--"the header and the body".
(That should be avoided, in my opinion.)  And Gnus uses a format
internally that it calls "header", which is what I'm talking about
here.  This is a 9-element vector, basically, with each header (ouch)
having one slot.

   These slots are, in order: `number', `subject', `from', `date',
`id', `references', `chars', `lines', `xref'.  There are macros for
accessing and setting these slots - they all have predictable names
beginning with `mail-header-' and `mail-header-set-', respectively.

   The `xref' slot is really a `misc' slot.  Any extra info will be put
in there.