2.13.0-RC1 changes

[ashawley]

I happened to try a recent build of the 2.13 compiler I built locally, and came across this error:

> ++2.13.0-M5-c2747e8
[info] Setting version to 2.13.0-M5-c2747e8
[info] Reapplying settings...
[info] Set current project to scala-xml (in build file:scala-xml/)
> xml/test:compile
[info] Updating {file:scala-xml/}xml...
[info] Resolving org.apache.commons#commons-lang3;3.5 ...
[info] Done updating.
[info] Compiling 85 Scala sources to scala-xml/jvm/target/scala-2.13.0-M5-c2747e8/classes...
[info] 'compiler-interface' not yet compiled for Scala 2.13.0-M5-c2747e8. Compiling...
[info]   Compilation completed in 19.068 s
[error] scala-xml/shared/src/main/scala-2.13/scala/xml/ScalaVersionSpecific.scala:29: method writeReplace overrides nothing
[error]   protected[this] override def writeReplace(): AnyRef = this
[error]                                ^

This is good news, since they may have fixed the serialization issue. We'll need to revert bd764f0 from #254.

[SethTisue]

in the 2.13 community build I'm using SethTisue@d7eb4fa

[SethTisue]

relevant Scala PR is scala/scala#7624