add syntactic sugar for match and match cases

[typeswitch-dev]

This PR adds syntactic sugar to match. In particular:

• you can use curly braces around the cases, instead of round ones, so match { ... } is equivalent to match ( ... )

• instead of writing the match cases as comma-separated arguments, you can write each case enclosed in curly braces. e.g. match( { A -> B } { C -> D } ) is the same as match( A -> B, C -> D ).

So the following are equivalent:

match ( A -> B, C -> D )
match { A -> B, C -> D }
match ( { A -> B } { C -> D } )
match { { A -> B } { C -> D } }

In addition the new cases syntax carries over to definitions, so for example you can write,

def foo {
   { A -> B }
   { C -> D }
}