MAJOR: handling of special comments.
MAJOR: handling of special comments.

Comments for marking: '(*BISECT-MARK*)' / '(*BISECT-VISIT*)'.
Comments for ignoring: '(*BISECT-IGNORE-BEGIN*)' / '(*BISECT-IGNORE-END*)' /
'(*BISECT-IGNORE*)'.

aantron/bisect_ppx,aantron/bisect_ppx