Remove unecessary tokens

[swfsql]

Since the postfix tokens are delimited, some right-hand tokens are not necessary.
The downside is the lost symmetry.
Making it optional is possible but may not be desirable.

1 ForLoop:

(0..3)::(for x in)
(0..3)::(for x)

2 Let:

(0, 1)::(let (a, b) =)
(0, 1)::(let (a, b))

3 Block (labelled)

{();}::('label:)
{();}::('label)