[CM] pre-parsing scheme code

[Woody Douglass]

Thanks for testing this! A factor of 2 is still nothing to sneeze at;
I'm running s7 on a resource-constrained embeddded machine, so I'll
take every cycle i can get at runtime!

On Mon, 2022-03-21 at 12:25 -0700, bil at ccrma.Stanford.EDU wrote:
> Gah -- I forgot to eval the expression in the second
> case -- then it's 1600, which is more what I expected.
> 
>    for (i = 0; i < 2000000; i++)
>      s7_eval(s, s7_list_nl(s, 4, s7_make_symbol(s, "list"),	\
> 	       s7_make_integer(s, 1),		\
> 	       s7_make_integer(s, 2),		\
> 	       s7_make_integer(s, 3),		\
> 	       NULL), s7_rootlet(s));
>