Check library/reflect bincompat against 2.11.0-RC1

Changes in the package scala.reflect.internals are ignored.
No longer generate deprecated dists/maven/latest/build.xml

The distpack-maven-* targets no longer create said dir/build.
Use the publish tasks directly instead.
Remove distribution building from ant build, see scala/scala-dist.

The only result of all this duplication was bitrot.
The main build is responsible for building, testing, documenting and publishing.
(It publishes everything needed to build a distribution to maven in
 `pack-maven.dist`.)

The sbt build over at scala/scala-dist handles distribution building for the
various platforms.

Note: after `ant build`, `build/pack` will have a pretty complete distribution.
(The only thing missing are the docs: see targets `pack.doc` and `docs.done`.)

To build your own distribution, do, e.g.:

```
ant publish-local-opt -Dmaven.version.suffix="-foo"
cd ~/git
hub clone scala/scala-dist
cd scala-dist
sbt 'set version := "2.11.0-foo"' 'set resolvers += Resolver.mavenLocal' universal:package-bin
```
Merge pull request #3600 from adriaanm/build-cleanup

Enable binary comp testing. Final build cleanup.