untyped macros beta 1

No spec yet, just docs at http://docs.scala-lang.org/overviews/macros/untyped-macros.html.
List of known issues: https://issues.scala-lang.org/secure/IssueNavigator.jspa?mode=hide&requestId=11912.
make use of UntypedType:
* Inferred type of macro defs
* Return type of macro types
tests for untyped macros
refactors macro tests
tests for untyped macros