specify the state of missing option flags in option dependencies

[zlin]

cat/foo[bar+] means if the bar option is missing, treat it as enabled cat/foo[bar-] means if the bar option is missing, treat it as disabled

Therefore, cat/foo[-bar-!?] means bar must be disabled if it is disabled for me. Treat it as disabled if it doesn't exist for foo.

[dleverton]

649c5a3ffc55