Motivation:
1. special handling of ByteBuf with multi nioBuffer rather than type of CompositeByteBuf (eg. DuplicatedByteBuf with CompositeByteBuf)
2. EpollDatagramUnicastTest and KQueueDatagramUnicastTest passed because CompositeByteBuf is converted to DuplicatedByteBuf before write to channel
3. uninitalized struct msghdr will raise error
Modifications:
1. isBufferCopyNeededForWrite(like isSingleDirectBuffer in NioDatgramChannel) checks wether a new direct buffer is needed
2. special handling of ByteBuf with multi nioBuffer in EpollDatagramChannel, AbstractEpollStreamChannel, KQueueDatagramChannel, AbstractKQueueStreamChannel and IovArray
3. initalize struct msghdr
Result:
handle of ByteBuf with multi nioBuffer in EpollDatagramChannel and KQueueDatagramChannel are ok
3c4dfed08a