Openocd branch

So, I put that in a branch because I had no idea how you'd want the directories and stuff laid out, and making sure it won't directly conflict with your setup since mine is slightly different (penguins everywhere).

If you think it's ok, then we can merge into master. Else we can keep it on the side for now.

It doesn't actually have any modification on the main files in mkstepper, so that it should be very easy to rebase it to the latest code development in master.

Maybe I should comment on what's there:

• embedded/build is where there's the Makefile to build my stuff on linux, with generic wildcards to all c files in mkstepper
• embedded/openocd is where there are the openocd configuration files
  • debug.cfg to run in duo with gdb, and
  • program.cfg to program the actual chip in one go
• embedded/samd51 are the ARM dependencies. I hesitated shipping that because technically, it'd be best if installed in the environment, but it's so small that I chose to have it in

There are two READMEs:

• build and
• openocd