Let's drop Scala 2.11 support from scala-xml and scala-parser-combinators

On the main branch, at least. If we needed to ship some really important bugfix later, it could always happen from a branch, especially if a volunteer was willing to handle it.


This is partly in the wake of Scala.js and Scala Native dropping 2.11 support, and partly just on general principle of making life easier for the volunteer maintainers and contributors lives easier in these repos.


Philippus Baalman points out that scala-xml actually dropped 2.11 support several years ago.

The fact that I forgot seems like evidence that it was a non-issue for people, which is encouraging.