[#2604] Not try to use sun.misc.Cleaner when on android

Motivation:

When a user tries to use netty on android it currently fails with "Could not find class 'sun.misc.Cleaner'"

Modification:

Encapsulate sun.misc.Cleaner usage in extra class to workaround this isssue.

Result:
Netty can be used on android again
Partially revert 4a13f66e131c3eb3d4293c198be0a613644d3a9c

Revert the removal of 'get' prefix from HTTP classes to ensure ABI
compatibility.  Note that this commit does not revert the changes in
SPDY, which is considered experimental.
Remove the deprecated methods in SPDY

SPDY is an experimental package. No need to keep ABI compatibility.
Enable verbose:gc only when 'leak' profile is disabled

The leak profile generates a lot of garbage which makes the verbose:gc
output too large.
Upgrade JACOCO to the latest version

.. to fix the build errors triggered by the old JACOCO release
[#2615] Correctly update SelectionKey after selector rebuild

Motivation:

When a select rebuild was triggered the reference to the SelectionKey is not updated in AbstractNioChannel. This will cause a CancelledKeyException later.

Modification:

Correctly update SelectionKey reference after rebuild

Result:

Fix exception
Let EpollReuseAddrTest also work with kernel versions that not have bugfix release part
Cleanup comment / code
fix example missing break statement in ReplayingDecoder
Maintain decoder result in HttpObjectAggregator

Motivation:
DecodeResult is dropped when aggregate HTTP messages.

Modification:

Make sure we not drop the DecodeResult while aggregate HTTP messages.

Result:

Correctly include the DecodeResult for later processing.