SI-7470 implements fundep materialization

This fix provides implicit macros with an ability to affect type inference
in a more or less sane manner. That's crucial for materialization of
multi-parametric type class instances (e.g. Iso's from shapeless).

Details of the technique can be found in comments. Also see the discussion
at https://github.com/scala/scala/pull/2499.
quasiquotes beta 1

No spec yet, just docs at http://docs.scala-lang.org/overviews/macros/quasiquotes.html.
List of known issues: https://issues.scala-lang.org/secure/IssueNavigator.jspa?mode=hide&requestId=11912.