Refactor JSInterop transformer state management
Fix #192: Fully support (sane uses) of scala.Enumeration

Note that this commit adds primitives for
scala.reflect.NameTransformer.MODULE_SUFFIX_STRING and
scala.reflect.NameTransformer.NAME_JOIN_STRING since
Enumeration.toString relies on them, but they rely on the
scala.sys.props infrastructure that we do not want to implement.
Merge pull request #196 from gzm0/enumerations

Fix #192: Fully support (sane uses) of scala.Enumeration
Merge branch 'master' into scala-2.11

Conflicts:
	compiler/src/main/scala/scala/scalajs/compiler/PrepJSInterop.scala