add LambdaCase

See LambdaCase (see also MultiWayIf, #77)

changed weight to 5

added Trac import task labels

assigned to @trac-none and unassigned @trac-ijones

changed title from create proposal for multi-way if or lambda case to add LambdaCase

changed the description

Trac metadata

Trac field	Value
Type	Task → Bug

added 1 deleted label and removed task label

changed milestone to %⊥

moving non-milestoned many year old legacy tickets out of the way

Set default priority (as this confuses Trac otherwise)

added enhancement modification labels and removed modification label

changed milestone to %Haskell 201x