Fix issue #19834: Support unpickling of exceptions pickled by Python 2.
Fix #19834: merge with 3.3.
Issue #19728: Fix sys.getfilesystemencoding() documentation
(Merge 3.3) Issue #19728: Fix sys.getfilesystemencoding() documentation
Issue #19833: asyncio doc: add class name to methods
Issue #19833: add 2 examples to asyncio doc (hello world)
Issue #19833: Document more asyncio.BaseEventLoop methods
asyncio: cleanup doc