misc: fix groff formatting nits in man pages

misc: fix groff formatting nits in man pages

Change a two-fonts macro to a one-font one, when there is only one
genuine argument.

Separate a punctuation mark or a section number from the only argument
to make two for a two-fonts macro.

Remove an unneeded escape in front of a horizontal tab character.

Correct the unit for distance from 'in' to 'i'.

Signed-off-by: Bjarni Ingi Gislason <bjarniig@rhi.hi.is>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>