Moved scaladoc sources into separate directory.
Moved scaladoc sources into separate directory.

This change is not externally visible. It moves the scaladoc
sources into src/scaladoc and adds an ant target for building
them. The compilation products are still packaged into
scala-compiler.jar as before, but with a small change to
build.xml a separate jar can be created instead.

SethTisue/scala-partest,scala/scala-partest,som-snytt/scala-partest,scala/scala-partest,lrytz/scala-partest