a2usbdsk ported to Raspberry Pi

I was able to port a2usbdsk to the Raspberry Pi quite easily due to it being based on libusb and libftdi. Really, I just had to set up a makefile. I had some issues getting it to open the FT232H though. libmpsse does not return any errors when attempting to open an FTDI device. This makes troubleshooting very difficult and frustrating. After adding some logging, I determined that the libftdi function ftdi_usb_open_desc_index() was returning error code -8, "get product description failed". Getting the product description is a pretty simple function and that error was not appearing on Mac OS X, so it left me baffled for a while. In the end, the issue was that Raspberry Pi/Linux strictly controls who can access USB devices. "sudo" got it running, but setting up a udev rule seems to be a better solution.

I have not tested this with a real Apple II yet, as my Platinum Apple //e was pretty much destroyed in a recent car accident due to air bag deployment. The case is shattered, but it may still work. I'll try this weekend.