New port: net/savvycan - CAN bus reverse engineering and capture tool

[leres]

Summary

My notes tell me this should be committed using:

${PORTSDIR}/Tools/scripts/addport

Proposted commit message:

This adds net/savvycan which is a CAN bus reverse engineering
and capture tool. It supports EVTV hardware, socketCAN compatible
devices, and other hardware.

Reviewed by: ? (mentor)
Approved by: ? (mentor)
Differential Revision: ?

[ler]

LGTM, and this falls within implicit, FWIW.