(map:left-square-bracket): Don't shift.

(map:left-square-bracket): Don't shift.
(map:left-curly-bracket): Don't shift.
(map:alt-2-7, map:ctrl-2-7): Deleted.
(map:alt-2, map:alt-7): New maps.
(state:init): Add `shift' to the branch actions of
`left-square-bracket' and `left-curly-bracket'.  Delete branches
alt-2-7 and ctrl-2-7, add branches alt-2 and alt-7.