check:mode and check:proc are unbound

[diamond-lizard]

When running the simplest of tests, like (check (+ 1 1) => 2), I get an error:

Error: unbound variable: check:mode

	Call history:

	<eval>	  (chicken.load#load-extension (##core#quote srfi-78) (##core#quote (srfi-78#)) (##core#quote require)...
	<syntax>	  (include "srfi-78-tests.scm")
	<syntax>	  (##core#include "srfi-78-tests.scm" #f)
	<syntax>	  (##core#begin (check (+ 1 1) => 2))
	<syntax>	  (check (+ 1 1) => 2)
	<syntax>	  (##core#if (>=74 check:mode75 1) (check:proc76 (quote77 (+ 1 1)) (lambda78 () (+ 1 1)) equal?71 2))
	<syntax>	  (>=74 check:mode75 1)
	<syntax>	  (check:proc76 (quote77 (+ 1 1)) (lambda78 () (+ 1 1)) equal?71 2)
	<syntax>	  (quote77 (+ 1 1))
	<syntax>	  (##core#quote (+ 1 1))
	<syntax>	  (lambda78 () (+ 1 1))
	<syntax>	  (##core#lambda () (+ 1 1))
	<syntax>	  (##core#begin (+ 1 1))
	<syntax>	  (+ 1 1)
	<syntax>	  (##core#undefined)
	<eval>	  (>=74 check:mode75 1)	<--

The fix is to (export (check check:mode).

After that, a chicken complains that check:proc is unbound, and there's a similar fix for that: (export (check check:proc))

It is important to do an (export (check check:mode)), which is called an "indirect export", rather than doing a simple (export check:mode), because the latter breaks encapsulation by allowing external access to the check:mode variable, while the former does not.