[#1626] Use static fields for default values
[#1628] Fix bug in ReadOnlyByteByteBufferBuf where get operations threw ReadOnlyBufferException
Fix up ChannelPipeline javadocs by add lost "don't "
[#1630] Fix re-entrance bug in ChannelOutboundBuffer.remove(...)
[#1624] Fix resource leak when writing to a closed / not-open channel
[#1606] Reduce overhead during writes because of ChannelPromise validation
Merge remote-tracking branch 'upstream/master'