[#2642] CompositeByteBuf.deallocate memory/GC improvement

Motivation:

CompositeByteBuf.deallocate generates unnecessary GC pressure when using the 'foreach' loop, as a 'foreach' loop creates an iterator when looping.

Modification:

Convert 'foreach' loop into regular 'for' loop.

Result:

Less GC pressure (and possibly more throughput) as the 'for' loop does not create an iterator
Upgrade to HTTP/2 draft 13

Motivation:

Need to upgrade HTTP/2 implementation to latest draft.

Modifications:

Various changes to support draft 13.

Result:

Support for HTTP/2 draft 13.
[#2647] Respect IOV_MAX when call writev in native transport

Motivation:

epoll transport fails on gathering write of more then 1024 buffers. As linux supports max. 1024 iov entries when calling writev(...) the epoll transport throws an exception.

Thanks again to @blucas to provide me with a reproducer and so helped me to understand what the issue is.

Modifications:

Make sure we break down the writes if to many buffers are uses for gathering writes.

Result:

Gathering writes work with any number of buffers
Fix JVM segfault during JNI call. Part of [#2647]

Motivation:
Currently when Native.writev(...) is used it is possible to see a JVM segfault because the offset is updated to early.

Modification:
Only update the offset once it is safe to do so.

Result:
No more segfault
Moved bit-level read operations from Bzip2Decoder to the new Bzip2BitReader

Motivation:

Collect all bit-level read operations in one class is better. And now it's easy to use not only in Bzip2Decoder. For example, in Bzip2HuffmanStageDecoder.

Modifications:

Created a new class - Bzip2BitReader which provides bit-level reads.
Removed bit-level read operations from Bzip2Decoder.
Improved javadoc.

Result:

Bzip2BitReader allows the reading of single bit booleans, bit strings of arbitrary length (up to 24 bits), and bit aligned 32-bit integers.
Adding payload to the Http2Client example.

Modifications:
When trying out the Http2Client example I noticed that adding a request
payload would not cause a data frame to written. This seems to be
because writeHeaders completes the promise, and then the writeData
call ends up in FlowControlWriter.writeFrame, isDone is true and
the data released and the call aborted and returned.
Adding a new promise for the writeData method allows a data frame to be
written.

Result:
A body/payload can now be sent to the server. The example was updated to
simply echo the payload received back to the calling client.
Add WebSocket Extension handlers for client and server.
Add permessage-deflate and deflate-frame WebSocket extension
implementations.

Motivation:

Need to compress HTTP WebSocket frames payload.

Modifications:

- Move UTF8 checking of WebSocketFrames from frame decoder to and
external handler.
- Change ZlibCodecFactory in order to use ZLib implentation instead of
JDK if windowSize or memLevel is different from the default one.
- Add WebSocketServerExtensionHandler and
WebSocketClientExtensionHandler to handle WebSocket Extension headers.
- Add DeflateFrame and PermessageDeflate extension implementations.
Fix buffer leak in test introduced by 282d6e73b82ec943a739201f7be1985c45ef032b
[#2643] Throw TooLongFrameException instead of using fireExceptionCaught

Motivation:

It's not always the case that there is another handler in the pipeline that will intercept the exceptionCaught event because sometimes users just sub-class. In this case the exception will just hit the end of the pipeline.

Modification:
Throw the TooLongFrameException so that sub-classes can handle it in the exceptionCaught(...) method directly.

Result:
Sub-classes can correctly handle the exception,
Fix checkstyle error introduced by 52cb55d3887034df778575799fdd00f174495809
Reuse previous created HttpHeaders by HttpObjectAggregator

Motivation:

HttpObjectAggregator currently creates a new FullHttpResponse / FullHttpRequest for each message it needs to aggregate. While doing so it also creates 2 DefaultHttpHeader instances (one for the headers and one for the trailing headers). This is bad for two reasons:
  - More objects are created then needed and also populate the headers is not for free
  - Headers may get validated even if the validation was disabled in the decoder

Modification:

- Wrap the previous created HttpResponse / HttpRequest and so reuse the original HttpHeaders
- Reuse the previous created trailing HttpHeader.
- Fix a bug where the trailing HttpHeader was incorrectly mixed in the headers.

Result:

- Less GC
- Faster HttpObjectAggregator implementation
[#2650] Allow to disable http header validation in SpdyHttpDecoder and SpdyHttpCodec

Motivation:

HTTP header validation can be expensive so we should allow to disable it like we do in HttpObjectDecoder.

Modification:

Add constructor argument to disable validation.

Result:
Performance improvement
[#2651] Fix possible infinite-loop when cancel tasks

Motivations:
In our new version of HWT we used some kind of lazy cancelation of timeouts by put them back in the queue and let them pick up on the next tick. This  multiple problems:
 - we may corrupt the MpscLinkedQueue if the task is used as tombstone
 - this sometimes lead to an uncessary delay especially when someone did executed some "heavy" logic in the TimeTask

Modifications:
Use a Lock per HashedWheelBucket for save and fast removal.

Modifications:
Cancellation of tasks can be done fast and so stuff can be GC'ed and no more infinite-loop possible
Fix over-sensible testcase
[#2653] Remove uncessary range checks for performance reasons

Motivation:

I introduced range checks as part of 6c47cc97111146396d2daf1a97051135d2eaf69e in some places. Unfortunally I also added some where these are not needed and so caused a performance regression.

Modification:

Remove range checks where not needed

Result:

Fixed performance regression.