[Snek] [keith-packard/snek] 07919c: Add lambda support

[Keith Packard]

  Branch: refs/heads/lambda
  Home:   https://github.com/keith-packard/snek
  Commit: 07919c7747f99e5f6e6d09b338966b4b182ba496
      https://github.com/keith-packard/snek/commit/07919c7747f99e5f6e6d09b338966b4b182ba496
  Author: Keith Packard <keithp at keithp.com>
  Date:   2021-03-23 (Tue, 23 Mar 2021)

  Changed paths:
    M snek-code.c
    M snek-exec.c
    M snek-gram.ll
    M snek-keyword.builtin
    M snek-parse.c
    M snek.h

  Log Message:
  -----------
  Add lambda support

This was an experiment to discover how much work this would involve,
which turned out to be 'not much'. As it consumes quite a bit of ROM
space, and doesn't seem to fit early programming education
environments, I've left it on a separate branch.

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