Fixed sending UDP and WS sending methods for packet limits

[lemunozm]

• WebSocket now can returns when send correctly a SendStatus::MaxPacketSizeExceeded instead of ResourceNotFound if the packet size is exceeded.
• UDP has increases the packet size when send.
  Now more bytes per packet can be sent if the OS let it.
• Exported some adapter constants dependent.
• Transport::max_message_size() now represents the teorical maximum size (see its related docs).