more: remove dead code and useless comments

more: remove dead code and useless comments

Removal of STOP requires explanation.  Looking unix-history-repo getline()
function in first BSD-3 version could return STOP.  By next tag BSD-4 the
return STOP had disappeared.  If I read this correctly that was a partial
removal, and second part has waited to be completed since 1980-11-16 when
BSD-4 was released.

Reference: https://github.com/dspinellis/unix-history-repo/blob/BSD-3-Snapshot-Development/usr/src/cmd/more.c#L501
Signed-off-by: Sami Kerola <kerolasa@iki.fi>