[Snek] [keith-packard/snek] c1fbbc: Report out of memory as a distinct error message

[Keith Packard]

  Branch: refs/heads/main
  Home:   https://github.com/keith-packard/snek
  Commit: c1fbbcec54ae54a87fb06b01dfb0b8ef40e957bf
      https://github.com/keith-packard/snek/commit/c1fbbcec54ae54a87fb06b01dfb0b8ef40e957bf
  Author: Keith Packard <keithp at keithp.com>
  Date:   2020-09-04 (Fri, 04 Sep 2020)

  Changed paths:
    M snek-parse.c

  Log Message:
  -----------
  Report out of memory as a distinct error message

Saying 'Syntax error: OOM' isn't very accurate.

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