LazyStandaloneCoroutine contains an val reference to block

[fvasco]

The class LazyStandaloneCoroutine set a private val reference to the block lambda.
This reference must be used only one time, but it cannot be reclaimed from GC until the Job instance is fully unreferenced.
Jobs, Deferreds and producers should release all potentially large references as soon at possible.

[elizarov]

The code looks good for me, but for consistency purposes it should be added to all LazyXxxCoroutine classes.

[fvasco]

This commit changes LazyDeferredCoroutine, LazyStandaloneCoroutine and LazyBroadcastCoroutine

[qwwdfsad]

ChannelCoroutine is not changed, but I think it is okay as they have a different usage pattern.
I'll merge it as soon as it pass all tests

fixed

[qwwdfsad]

Thanks!