Fix chunk type for stream identifier

Motivation:
The problem with the current snappy implementation is that it does
not comply with framing format definition found on
https://code.google.com/p/snappy/source/browse/trunk/framing_format.txt

The document describes that chunk type of the stream identifier is defined
as 0xff. The current implentation uses 0x80.

Modifications:
This patch replaces the first byte of the chunk type of the stream identifier
with 0xff.

Result:
After this modification the snappy implementation is compliant to the
framing format described at
https://code.google.com/p/snappy/source/browse/trunk/framing_format.txt.
This results in a better compatibility with other implementations.
Feed only a single SSL record to SSLEngine.unwrap()

Motivation:

Some SSLEngine implementations violate the contract and raises an
exception when SslHandler feeds an input buffer that contains multiple
SSL records to SSLEngine.unwrap(), while the expected behavior is to
decode the first record and return.

Modification:

- Modify SslHandler.decode() to keep the lengths of each record and feed
  SSLEngine.unwrap() record by record to work around the forementioned
  issue.
- Rename unwrap() to unwrapMultiple() and unwrapNonApp()
- Rename unwrap0() to unwrapSingle()

Result:

SslHandler now works OpenSSLEngine from finagle-native.  Performance
impact remains unnoticeable.  Slightly better readability. Fixes #2116.
Stop ThreadLocalRandom's initial seed generation immediately on interruption

Motivation:

ThreadLocalRandomTest reveals that ThreadLocalRandom's initial seed generation loop becomes tight if the thread is interrupted.
We currently interrupt ourselves inside the wait loop, which will raise an InterruptedException again in the next iteration, resulting in infinite (up to 3 seconds) exception construction and thread interruptions.

Modification:

- When the initial seed generator thread is interrupted, break out of the wait loop immediately.
- Log properly when the initial seed generation failed due to interruption.
- When failed to generate the initial seed, interrupt the generator thread just in case the SecureRandom implementation handles it properly.
- Make the initial seed generator thread daemon and handle potential exceptions raised due to the interruption.

Result:

No more tight loop on interruption.  More robust generator thread termination. Fixes #2412
Use correct generics for TCP_KEEPIDLE, TCP_KEEPINTVL and TCP_KEEPCNT in EpollChannelOption. Part of [#2396]

Motivation:
Currently the generics used for TCP_KEEPIDLE, TCP_KEEPINTVL and TCP_KEEPCNT are incorrect.

Modifications:
Use Integer as type

Result:
User can use TCP_KEEPIDLE, TCP_KEEPINTVL and TCP_KEEPCNT as expected
[#2400] Not close LocalChannel during deregister()

Motivation:
At the moment it is not possible to deregister a LocalChannel without close it.

Modification:
Not close the LocalChannel during dergister

Result:
It will be possible in the future to deregister a LocalChannel and register it to another EventLoop
[#2414] Fix RuntimeException during modify events via EpollEventLoop

Motivation:
We are currently try to modify the events via EpollEventLoop even when the channel was closed before and so the fd was set to -1. This fails with a RuntimeException in this case.

Modification:
Always check if the Channel is still open before try to modify the events.

Result:
No more RuntimeException because of a not open channel
[#2414] Fix IllegalStateException when try to configure AbstractEpollChannel once it is deregistered

Motivation:
AbstractEpollChannel.clearEpollIn() throws an IllegalStateException if a user tries to change the autoRead configuration for the Channel and the Channel is not registered on an EventLoop yet. This makes it for example impossible to set AUTO_READ to false via the ServerBootstrap as the configuration is modifed before the Channel is registered.

Modification:
Check if the Channel is registered and if not just modify the flags directly so they are respected once the Channel is registered

Result:
It is possible now to configure AUTO_READ via the ServerBootstrap
Make NioSocketChannelTest more bullet-proof

Motivation:
I had the NioSocketChannelTest.testFlushCloseReentrance() fail sometimes on one of my linux installation. This change let it pass all the time.

Modification:
Set the SO_SNDBUF to a small value to force split writes

Result:
Test is passing all the time where it was sometimes fail before.
Mark sun.nio.ch as optional

Motivation:

If sun.nio.ch is not optional this will cause troubles in the
OSGi world. The package is not exposed by default in OSGi, so
actually the whole netty framework cannot be used directly.

There are workarounds, but workarounds are ugly. Especially since
the use of sun.nio.ch is optional. So the requirement on the
package should be optional as well.

Modifications:

Make the import of sun.nio.ch optional.

Result:

If the package cannot be imported it will behave as if the package
sun.nio.ch is not present (like with other JVMs). If the package is
exposed in OSGi (e.g. bootclassloader delegation, extension fragment)
it will be used.
[codec-memcache] Avoid NPE on channelInactive.

Motivation:
When no currentMessage has been set and the channel is inactive, a NPE is raised.

Modification:
Make sure that a currentMessage is available before checking the extras.

Result:
No more NPE raised potentially.
Resurrect channel deregistration and constructor changes

Motivation:

Due to the complexity of handling deregistration and re-registration of
a channel, we previously decided to remove the deregister() operation
completely to simplify our code.  However, we realized that it shouldn't
be that complicated to implement it during our discussion about making
I/O scheduling more flexible and more customizable [1], and thus the
removal of deregistration and re-registration is unnecessary now.

Modification:

- Revert commit c149f4bcc0c0d02aa1abcd5e39c155a9e598822e
- Revert commit e743a27e752f0badaf71688457793d0aa365a3ac
- Make some additional adjustments

Result:

- deregister(), fireChannelUnregistered(), and channelRegistered() were
  added back..
- Channel constructors do not require an EventLoop anymore.

[1] https://github.com/netty/netty/issues/2250
Synchronized between 4.1 and master

Motivation:

4 and 5 were diverged long time ago and we recently reverted some of the
early commits in master.  We must make sure 4.1 and master are not very
different now.

Modification:

Fix found differences

Result:

4.1 and master got closer.
Synchronized between 4.1 and master

Motivation:

4 and 5 were diverged long time ago and we recently reverted some of the
early commits in master.  We must make sure 4.1 and master are not very
different now.

Modification:

Fix found differences

Result:

4.1 and master got closer.
Remove unused method to match up 4.1 branch

 Motivation:

4 and 5 were diverged long time ago and we recently reverted some of the
early commits in master.  We must make sure 4.1 and master are not very
different now.

Modification:

Remove ChannelHandlerInvokerUtil.invokeWriteAndFlush(...) as it is not used anyway and not exists in 4.1

Result:

4.1 and master got closer.
Synchronized between 4.1 and master again (part 2)

Motivation:
4 and 5 were diverged long time ago and we recently reverted some of the
early commits in master.  We must make sure 4.1 and master are not very
different now.

Modification:
Remove ChannelHandlerInvoker.writeAndFlush(...) and the related
implementations.

Result:
4.1 and master got closer.
Fix compilation errors
Synchronized between 4.1 and master (part 3)

Motivation:

4 and 5 were diverged long time ago and we recently reverted some of the
early commits in master.  We must make sure 4.1 and master are not very
different now.

Modification:

Fix found differences

Result:

4.1 and master got closer.
Undeprecate deregister() and chanelUnregistered()

Motivation:

As discussed in #2250, it will become much less complicated to implement
deregistration and reregistration of a channel once #2250 is resolved.
Therefore, there's no need to deprecate deregister() and
channelUnregistered().

Modification:

- Undeprecate deregister() and channelUnregistered()
- Remove SuppressWarnings annotations where applicable

Result:

We (including @jakobbuchgraber) are now ready to play with #2250 at
master
Code clean-up

Motivation:

It is less confusing not to spread Thread.interrupt() calls.

Modification:

- Comments
- Move generatorThread.interrupt() to where currentThread.interrupt() is
  triggered

Result:

Code that is easier to read
Eliminate unnecessary extra synchronization in DefaultChannelPipeline

Motivation:
At the moment whenever we add/remove a ChannelHandler with an EventExecutorGroup we have two synchronization points in the execution path. One to find the childInvoker and one for add/remove itself. We can eliminate the former by call findIInvoker in the synchronization block, as we need to synchronize anyway.

Modification:
Remove the usage of AtomicFieldUpdater and the extra synchronization in findInvoker by moving the call of the method in the synchronized(this) block.

Result:
Less synchronization points and volatile reads/writes