constructors on heap, consuming match, move modifier in reference expression, .bring. keyword to return from block, some fixes

tests/match.lang

@@ -1,6 +1,7 @@
 decl fruit_cost : Fruit -> Int
 def fruit_cost : fruit = {
-  return (match fruit with
+  var fruit_copy = fruit
+  return (match <- fruit_copy with // consuming match
       | $Banana -> 11
       | $Apple | $Orange -> 7)
 }