Scala 2.11 modules now under org.scala-lang.modules

Using 1.0-RC2 for scala-xml, 1.0-RC1 for scala-parser-combinators.
Update dependencies to Scala 2.11.0-M7.

I had to sprinkle some excludes due to dependency of scala-compiler M7 on
M6 modules. Those excludes won't be needed by the time M8 is out.
Merge pull request #1092 from gkossakowski/scala-2.11-compat

Build for Scala 2.11