datapath-windows: Introduce bridge-internal ports.

In this patch, we provide explanation and the reasoning for
bridge-internal ports. The code to add such a port in come in later
patch in the series.

We also fix some formatting issues in PacketIO.c.

Signed-off-by: Nithin Raju <nithin@vmware.com>
Acked-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Tested-by: Alin Gabriel Serdean <aserdean@cloudbasesolutions.com>
Acked-by: Ankur Sharma <ankursharma@vmware.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>