Prepare removal of scala-xml, scala-parser-combinators

Every test deleted here has found its way to the respective
repositories of scala-xml and scala-parser-combinators,
where they will continue to be tested with partest.

The modified tests became independent of these modules,
as they should've been from the start.
Remove scala-xml and scala-parser-combinators

These modules move to their own repositories:
  - https://github.com/scala/scala-xml (v1.0-RC3)
  - https://github.com/scala/scala-parser-combinators (v1.0-RC1)

The modularization depends on the new partest, as the old one's
classpath handling did not support a modularized scala.

The compiler pom now depends on the artifacts published separately,
with versions specified in versions.properties.

NOTES:
  - The osgi tests resolve the xml and parsers jars and osgi-fy them,
    as they are no longer built locally.
    TODO: Can we move the osgification to the module builds?
  - Disabled local repositories: don't want to accidentally include
    unpublished artifacts in releases etc.
Don't use sonatype to resolve jars relevant to a release.

To eliminate any delay between deploying partest to sonatype
and using it for development, we resolve it through sonatype.

Not acceptable for jars that ship as part of the release,
such as scaladoc (we'd see a jar others might not see).
Include xml and parsers in dist, tool classpath.

This brings the external modules (xml, parsers)
back to the classpaths of build/(quick|pack)/bin/scala*.

Include the OSGIfied jars for external modules in dist.
(TODO: OSGI-fy externally)

Download javadoc/sources from maven and include in dist.
Fix dbuild meta info: remove scaladoc project

That is, scaladoc is still in the scala-compiler artifact.
Let dbuild know so that it won't freak out.

ps: dbuild-meta.json should be kept in synch with
    src/build/dbuild-meta-json-gen.scala until we can
    automate that in the build
Merge pull request #2855 from adriaanm/modularize-xml-parsers

Modularize: xml & parser-combinators