MFC r1.6 r1.30 r1.28 (HEAD):

MFC r1.6 r1.30 r1.28 (HEAD):
 * fix markup of `auto' argument
 * add `auto' where missing
 * delete extra synopsis
 * fix wrong single character quoting

Minor wording improvement.

Add an example os how to change label format from 32 bit to 64 bit,
and delete note that it require reboot.

Fix typo: missing line break, which got .Xr hide sentence.

Update disklabel doc:
 - Sync usage() to disklabel.8
 - Add note that this is 32 bit disklabel
 - Move description of `-f' flag from unrelated section (SAVED FILE FORMAT)
 - Improve some wording and mark up a bit