[#1614] Fix bug in SingleThreadEventExecutor which prevent scheduled tasks to get executed

The problem was that with OioSocketChannel there was always a read Task in the taskQueue and with the old logic it never tried to execute scheduled tasks if there was at least one task in the taskQueue.
minor documentation cleanup
netty-1597: Rewrite ByteBufInputStream.readLine() to avoid IndexOutOfBoundsException and to behave more correctly for lines ending in '\r'.
Fix checkstyle
netty-1616: Adding a 'last' check to SpdyHttpEncoder.
[#1619] Fix bug in ChannelOutboundBuffer which could lead to invalid write order when fireChannelWritabilityChanged() write another message
Make PendingWrites recyclable to reduce GC pressure
[#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
Fix types in javadocs
[#1612] Allow to disable resource leak detection via API
Remove ResourceLeakDetector.ENABLED / Replace ResourceLeakDetector.is/setDisabled() with is/setEnabled()

- Related: #1612
Remove an unnecessary empty line
[#1637] Check for null parameters
Fix compile error
Simplify the validation logic proposed in 25f96b164498988439c38baf6ff4c57763464824