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.

Author: adriaanm