[Snek] [keith-packard/snek] 146480: Add port to SiFive HiFive1 revb

[Keith Packard]

  Branch: refs/heads/hifive1-revb
  Home:   https://github.com/keith-packard/snek
  Commit: 14648023c85e695ba55c113d8364593315cecf38
      https://github.com/keith-packard/snek/commit/14648023c85e695ba55c113d8364593315cecf38
  Author: Keith Packard <keithp at keithp.com>
  Date:   2019-11-18 (Mon, 18 Nov 2019)

  Changed paths:
    A ports/hifive1revb/.gitignore
    A ports/hifive1revb/Makefile
    A ports/hifive1revb/snek-hifive1revb.builtin
    A ports/hifive1revb/snek-metal-gpio.c
    A ports/hifive1revb/snek-metal-uart.c
    A ports/hifive1revb/snek-metal.c
    A ports/hifive1revb/snek-metal.h

  Log Message:
  -----------
  Add port to SiFive HiFive1 revb

This references freedom-e-sdk remotely, so building will
require that be available.

Signed-off-by: Keith Packard <keithp at keithp.com>