Goals:
* Make the set of combinators clearer and smaller.
* Solve a number of issues, such as those about parse failures related to
patterns.
* Solve the bug from #244.
The idea is very simple, we stop doing this
( foo
, bar
)
and start doing this
( foo,
bar
)
* We switch to trailing commas which solves the indentation issues for
patterns automatically.
* The new general ‘sep’ combinator finally is clear enough, and all the old
zoo of ‘velt’ and ‘velt'’ and ‘sepWith’, etc. which was confusing and
overlapping goes away.
