Fixes SI-4909 and SI-5763
Fixes SI-4909 and SI-5763

Finally, -sourcepath is split into:
-Ysourcepath     - for the library bootstrapping
-doc-source-path - for scaladoc links to source code

(squished the resident compiler test fix into this commit)

Review by @jsuereth.

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