[Snek] [keith-packard/snek] 54d196: Use strfromf instead of sprintf for floats

[Keith Packard]

  Branch: refs/heads/main
  Home:   https://github.com/keith-packard/snek
  Commit: 54d1962bc26923a59c43ce1d143be2cdc4d99ef4
      https://github.com/keith-packard/snek/commit/54d1962bc26923a59c43ce1d143be2cdc4d99ef4
  Author: Keith Packard <keithp at keithp.com>
  Date:   2021-06-20 (Sun, 20 Jun 2021)

  Changed paths:
    M chips/atmega/snek-atmega.h
    M chips/avr/snek-avr.h
    M snek-print.c
    M snek.h

  Log Message:
  -----------
  Use strfromf instead of sprintf for floats

This ensures conversion of float without going through double.

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