Make @Suspendable work on lambdas again in Kotlin M13

[aristotaloss]

Adds a new annotation (co.paralleluniverse.kotlin.fibers.Suspendable) in Kotlin using the new Kotlin runtime target and retention API to allow putting @Suspendable on lambdas as per before M13.

Example:

import co.paralleluniverse.kotlin.fibers.Suspendable

@Suspendable {
    Fiber.sleep(100)
    println("Hello")
}

The functionality described above broke when M13 required explicit annotation targeting to expressions in order to use them on Lambdas. To solve this, I have created a simple new annotation under the quasar-kotlin module which will also be recognized as instrument hinting to mark suspendable functions or lambdas.

This closes #121 if merged.

[aristotaloss]

Note: I have signed the electronic agreement on contributing.

[circlespainter]

Solved in a different way with later Kotlin releases, thanks for the contribution!