Use ftdi driver instead of ft2232 for OpenOCD debugger.
Set master AF status on PIC32 before individual filters.

The AF is reset every time you re-configure the filter mask, so this was
erasing all of the filters we just configured. Wish I had a test for
this but it has to run on the PIC32 to really know.

Fixed #237.
Use separate filter masks for STD and EXT CAN IDs on PIC32.
Pass CAN AF format through to the platform so it can init properly.
Count CAN filter indicies from 0, not 1.

This fixes AF filter initialization on the PIC32.

Fixed #237.
On PIC32, count filters across all buses to avoid conflicts.
Fix test signals configuration, initializing const members.