Improve the randomness of ThreadLocalRandom for all platform

- Fixes #1765
Java 6 did a poor job of generating seedUniquifier unlike 7, so I implemented platform-independent seedUniquifier generator with configurability
Make AbstractBootstrap public

.. to work around the issue with JDK reflection described here:

  http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4283544

Fixes #1780
SPDY: allow MAX_CONCURRENT_STREAMS to be set to 0
[#1782] Fix IndexOutOfBoundException with direct buffer and gathering writes
[#1777] Use correct Thread when close per channel
Small code improvements
[#1735] Disable usage of JdkZlibDecoder by default, will be enabled in 4.1.0.Final
@deprecated all methods which are related to deregister as it will be removed in 4.1.0.Final
[maven-release-plugin] prepare release netty-4.0.8.Final
[maven-release-plugin] prepare for next development iteration
Bump up version to 4.1.0.Alpha1-SNAPSHOT
[#1785] Fix incorrect javadocs
ability to use Executor instead of ThreadFactory
Currently the system variable to chose which type of zlib decoder is being negated
HTTP Chunk, wrong delimiter written
[#1792] PlatformDependent.freeDirectBuffer(..) now respect hasUnsafe()
[#1788] Correctly decode CRC32 and ISIZE when using JdkZlibDecoder

Because of incorrect decoding a CompressionException was thrown before
Free up all buffers after the tests
[#1797] Throw IllegalArgumentException if AbstractByteBuf.skipBytes(...) is used with a negative value
[#1798] Correctly handle skipping of too big frames