Based on https://github.com/scala/scala-collection-compat/blob/master/compat/src/main/scala-2.11_2.12/scala/collection/compat/PackageShared.scala
but reproduced here so we don't need to add a dependency on this library. It contains much more than we need right now, and is
not promising binary compatibility yet at the time of writing.
INTERNAL API
Based on https://github.com/scala/scala-collection-compat/blob/master/compat/src/main/scala-2.11_2.12/scala/collection/compat/PackageShared.scala but reproduced here so we don't need to add a dependency on this library. It contains much more than we need right now, and is not promising binary compatibility yet at the time of writing.