unfork Akka for 2.13

[SethTisue]

or rather, use the same fork we use in 2.12

[SethTisue]

but this will have to wait until I fix genjavadoc

[SethTisue]

but this will have to wait until I fix genjavadoc

I fixed genjavadoc today, but now scala-java8-compat is the blocker

[SethTisue]

attempting to unfork for 2.12, first, at #865

[SethTisue]

@ennru points out that Akka has already published for M5, so why wouldn't it be green here?

scala-java8-compat has published for M5 as well, though @Ichoran is still working on scala/scala-java8-compat#113

it's now close enough to 2.13.0-RC1 release time that I should probably look for a way to work around this in the community build somehow, rather than wait for Rex (I already did such a workaround once, e.g.
scala/scala-java8-compat#113 (comment))

[SethTisue]

We used a branch of Lukas's. The Akka team is working on publishing for RC1; once they publish we ought to be able to unfork.

[SethTisue]

rather than keep this ticket open, I think it's fine to just assume I'll get to it in the course of my usual rounds