OperatorBuffer

[akarnokd]

Operator Buffer, split into 4 variants.

Issue #1060.

There are some important behavioral changes compared to the original versions:

• When an onError event appears from anywhere, the currently accumulated chunk(s) are NOT emitted before the error is propagated. This conforms with Rx Design Guideline 6.6.
• The Observable returned by the Func0 inside the buffer(Func0<Observable<B>>) now is used as long as possible and whenever it fires an event, a new buffer chunk is started. The Func0 is called only once per subscriber. The original called it and subscribed to it all the time, causing all-increasing resubscriptions.

[cloudbees-pull-request-builder]

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