so I took the liberty to 'privatize' them with a leading underscore.
This also completely removes '_ArrayBody' from the public interface.
Should be NFC, apart from the public interface change.
Swift SVN r18625
-Hide vars that have a private type.
-Hide functions that have a parameter with private type or a parameter name with leading underscore.
-Minor change in StringUTF16.swift to avoid printing "func generate() -> IndexingGenerator<_StringCore>".
rdar://17027294
Swift SVN r18623