mkfs: getbool is redundant

mkfs: getbool is redundant

getbool() can be replaced with getnum_checked with appropriate
min/max values set for the boolean variables. Make boolean
arguments consistent - all accept 0 or 1 value now.

[ Eric Sandeen <sandeen@redhat.com>: manpage tidiness ]

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Jan Tulak <jtulak@redhat.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>