afsd: Update list of supported flags

afsd: Update list of supported flags

afsd.c starts with a block comment listing the flags supported by the
afsd command.  As the code has evolved this list has not been kept up
to date.  Bring the list up to date.  Some obsolete options no longer
have any backing code.  These are marked OBSOLETE.  Some obsolete
options have code that says they are now deprecated.  These are
marked IGNORED.

Additionally fix a typo in backuptree's help text.

Change-Id: I90ddf4db826c891bf1daf6959f94feee17d35f78
Reviewed-on: http://gerrit.openafs.org/11857
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Daria Brashear <shadow@your-file-system.com>