0.10-rc: Mutex & Kotlin RC

• Switched to Kotlin version 1.1.0-rc-91.
• Mutex synchronization primitive is introduced.
• buildChannel is renamed to produce, old name is deprecated.
• Job.onCompletion is renamed to Job.invokeOnCompletion, old name is deprecated.
• delay implementation in Swing, JavaFx, and scheduled executors is fixed to avoid an extra dispatch.
• CancellableContinuation.resumeUndispatched is introduced to make this efficient implementation possible.
• Remove unnecessary creation of CancellationException to improve performance, plus other performance improvements.
• Suppress deprecated and internal APIs from docs.
• Better docs at top level with categorized summary of classes and functions.