Add UDP & IPV6 support + some fix

[spawn451]

ncLines.pas:

• Fix Linux compilation
• Added UDP support
• Added IPV6 support

ncSockets.pas:

• Defined DefReadBufferLen as a new property
• Ajust TncCustomTCPServer.DataSocketDisconnected
• Explicitly set this unit to use TCP
• Update Client Send method so data cannot be send while socket is inactive
• Added IPV6 support

ncSources.pas:

• Explicitly set this unit to use TCP
• Added IPV6 support

ncUDPSockets.pas:

• UDP implementation with Broadcast option
• Added new SimpleSockets_UDP demo
• Updated the SimpleSockets demo