Investigate: make private methods public to enable inlining

[lrytz]

The old optimizer makes synthetic and paramaccessor methods public to enable inlining methods that invoke them.

https://github.com/scala/scala/blob/2.11.x/src/compiler/scala/tools/nsc/backend/opt/Inliners.scala#L659

[retronym]

See also: https://github.com/scala/scala/blob/2.11.x/src/compiler/scala/tools/nsc/typechecker/SuperAccessors.scala#L248-L254

[lrytz]

discussion, linked from Jason's reference https://groups.google.com/forum/#!topic/scala-internals/iPkMCygzws4

see also scala/scala@e6b4204