Implemented LZ4 compression codec

Motivation:

LZ4 compression codec provides sending and receiving data encoded by very fast LZ4 algorithm.

Modifications:

- Added `lz4` library which implements LZ4 algorithm.
- Implemented Lz4FramedEncoder which extends MessageToByteEncoder and provides compression of outgoing messages.
- Added tests to verify the Lz4FramedEncoder and how it can compress data for the next uncompression using the original library.
- Implemented Lz4FramedDecoder which extends ByteToMessageDecoder and provides uncompression of incoming messages.
- Added tests to verify the Lz4FramedDecoder and how it can uncompress data after compression using the original library.
- Added integration tests for Lz4FramedEncoder/Decoder.

Result:

Full LZ4 compression codec which can compress/uncompress data using LZ4 algorithm.
Rename SnappyFramedEncoder/Decoder to SnappyFrameEncoder/Decoder

Related issue: #2766

Motivation:

Forgot to rename them before the final release by mistake.

Modifications:

Rename the classes

Result:

Better naming
Reduce the fallback SOMAXCONN value

Related issue: #2407

Motivation:

The current fallback SOMAXCONN value is 3072.  It is way too large
comparing to the default SOMAXCONN value of popular OSes.

Modifications:

Decrease the fallback SOMAXCONN value to 128 or 200 depending on the
current OS

Result:

Saner fallback value
Add socksx package which supports SOCKS 4/4a/5

Motivation:

SOCKS 4 and 5 are very different protocols although they share the same
name.  It is not possible to incorporate the two protocol versions into
a single package.

Modifications:

- Add a new package called 'socksx' to supercede 'socks' package.
- Add SOCKS 4/4a support to the 'socksx' package

Result:

codec-socks now supports all SOCKS versions
Overall clean-up on socksx package

- SocksV[45] -> Socks[45]
- Make encodeAsByteBuf package private with some hassle
- Split SocksMessageEncoder into Socks4MessageEncoder and
  Socks5MessageEncoder, and remove the original
- Remove lazy singleton instantiation; we don't need it.
- Remove the deprecated methods
- Fix Javadoc errors
Allow ChunkedInput to provide the progress of its transfer

Related issue: #2741 and #2151

Motivation:

There is no way for ChunkedWriteHandler to know the progress of the
transfer of a ChannelInput. Therefore, ChannelProgressiveFutureListener
cannot get exact information about the progress of the transfer.

If you add a few methods that optionally provides the transfer progress
to ChannelInput, it becomes possible for ChunkedWriteHandler to notify
ChannelProgressiveFutureListeners.

If the input has no definite length, we can still use the progress so
far, and consider the length of the input as 'undefined'.

Modifications:

- Add ChunkedInput.progress() and ChunkedInput.length()
- Modify ChunkedWriteHandler to use progress() and length() to notify
  the transfer progress

Result:

ChunkedWriteHandler now notifies ChannelProgressiveFutureListener.
[#2769] Fix regression when writing different message types

Motivation:

Due a regression NioSocketChannel.doWrite(...) will throw a ClassCastException if you do something like:

channel.write(bytebuf);
channel.write(fileregion);
channel.flush();

Modifications:

Correctly handle writing of different message types by using the correct message count while loop over them.

Result:

No more ClassCastException
[#2771] Correctly handle constructing of EmbeddedChannel

Motivation:

Because of an incorrect logic in teh EmbeddedChannel constructor it is not possible to use EmbeddedChannel with a ChannelInitializer as constructor argument. This is because it adds the internal LastInboundHandler to its ChannelPipeline before it register itself to the EventLoop.

Modifications:

First register self to EventLoop before add LastInboundHandler to the ChannelPipeline.

Result:

It's now possible to use EmbeddedChannel with ChannelInitializer.
Fix the regression caused by f31c630c8cc15c4de1cc7e45b6c5c8053d5bcb75

f31c630c8cc15c4de1cc7e45b6c5c8053d5bcb75 was causing
SocketGatheringWriteTest to fail because it does not take the case where
an empty buffer exists in a gathering write.

When there is an empty buffer in a gathering write, the number of
buffers returned by ChannelOutboundBuffer.nioBuffer() and the actual
number of write attemps can differ.

To remove the write requests correctly, a byte transport must use
ChannelOutboundBuffer.removeBytes()
Fix a bug where ChannelOutboundBuffer.removeBytes() throws ClassCastException

When a ChannelOutboundBuffer contains ByteBufs followed by a FileRegion,
removeBytes() will fail with a ClassCastException.  It should break the
loop instead.
Fix for issue #2765 relative to unstable trafficshaping test procedure

Motivation:

The test procedure is unstable due to not enough precise timestamping
during the check.

Modifications:

Reducing the test cases and cibling "stable" test ("timestamp-able")
bring more stability to the tests.

Result:

Tests for TrafficShapingHandler seem more stable (whatever using JVM 6,
7 or 8).
Fix checkstyle