moves analyzer.ImportType into scala.reflect.internal

This cute little type is necessary for importers to work correctly.
I wonder how we could overlook its existence for almost 2 years.
deprecates resetAllAttrs and resetLocalAttrs in favor of the new API

We now have c.untypecheck, which is supposed to be a counterpart of c.typecheck
in the sense that it goes back from typed trees to untyped ones:
http://stackoverflow.com/questions/20936509/scala-macros-what-is-the-difference-between-typed-aka-typechecked-an-untyped.

Let’s hope that c.untypecheck will soon be able to solve our problems
with partially/incorrectly attributed trees emitted by macros:
https://groups.google.com/forum/#!topic/scala-internals/TtCTPlj_qcQ.