The GNU style double-dashes collide with MH's command line concepts.
It makes no sense to simply allow a second dash, because all the
rest is different. (Think of `pick --component'.) It's more important
to keep the concepts clean than trying to imitate different concepts.
OPTIONS
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-* change switches to accept two dashes (--help)
* can we move option checking to its own function? Currently each
command is doing that itself.
* make the option parsing code dynamic, so that there is no limit