examples: net: Sniffer application

This is simple sniffer application coming a long with script taken and adapted from @malvira to pipe the sniffed output into Wireshark. So far it's only tested for the MSB-A2.
See http://www.abxsoft.com/misra/m79.html#func79c, but I will remove it anyway, since (a) we're not using it at other places and (b) [Comments on the MISRA C coding guidelines](http://www.knosof.co.uk/misracom.html) say: "This is a nonsense rule."