Same issue as fixed#1733 for ByteToMessageHandler.
### Motivation:
`NIOSingleStepByteToMessageProcessor` called out to the decoder's shouldReclaimBytes method after every parsing attempt, even if the decoder returned a value (which means continue in the `decodeLoop`).
That's quite pointless because we won't add any bytes into the buffer before we're trying the decoder again. Further it is a huge performance penalty for a use-cases in which we only consume small frames from the buffer. (Like reading data rows in a database client)
### Modifications:
- Only ask the decoder if we should reclaim bytes if the decoder actually is not able to process more frames from the input buffer.
Motivation:
The remaining NIO code really conceptually belongs in a module called
NIOPosix, and NIOCore should really be called NIO. We can't really do
that last step, but we can prepare by pushing the bulk of the remaining
code into a module called NIOPosix.
Modifications:
- Move NIO to NIOPosix
- Make NIO an umbrella module.
Result:
NIOPosix exists.
Fabian Fett