[vpm] emitting switches -- BodyTreeMaker

1) introduce BodyTreeMaker to get rid of special casing for body
   now each case is a list of TreeMakers rather than a pair of such a list and a tree
   needed to do this since emitting switches requires access to the untranslated body

2) emitting switches
    - alternatives are flattened: each alternative block ends with a jump to the next alternative (if there is one)
    - to avoid stack overflow in typedMatch: detect when translateMatch returns a Match

the patch to uncurry would be nicer with an extractor, but that breaks due to a bug in old patmat

made trees into dags again -- NPE in erasure

tree.duplicate seems to break lambdalift because it
does not give fresh symbols (or trees?) to the valdefs
for the arguments of duplicated functions

duplicate enclosing tree, not subtrees

improved propagateSubstitution for AlternativesTreeMaker

 - it now propagates to all its alternatives, so we don't have to do that in chainBefore
 - by making propagation more regular, a bug in substitution in AlternativesTreeMaker manifested itself
   it introduced a new binder, unnecessarily, which then was unbound -- now reusing binder of outer pattern

having removeSubstOnly in propagateSubstitution unveiled a bug: guard treemaker should substitute

move fixerUpper closer to what it fixes up

1 files changed, 2 insertions, 1 deletions

diff --git a/test/files/run/virtpatmat_literal.scala b/test/files/run/virtpatmat_literal.scala
index cb72b1d2a5..5bd6b30791 100644
--- a/test/files/run/virtpatmat_literal.scala
+++ b/test/files/run/virtpatmat_literal.scala
@@ -1,8 +1,9 @@
 object Test extends App {
+ val a = 1
  1 match { 
    case 2 => println("FAILED") 
    case 1 => println("OK") 
-   case 1 => println("FAILED") 
+   case `a` => println("FAILED") 
  }
 
  val one = 1