Removed pos/run test

Most of the pos tests were incorporated in the ShouldCompile 'unit test'.
The others are going back to scala/scala.

I was a bit overzealous in moving stuff over to scala-xml
in scala/scala#9c50dd5. These were all compiler tests that
accidentally touched on xml. I've tried to delicately decouple them
so they can roam the scalac pastures as intended.
Converted the last of the run tests.