* scripts/README, scripts/hello.scm, safe/untrusted.scm,

	* scripts/README, scripts/hello.scm, safe/untrusted.scm,
	safe/evil.scm, safe/README, modules/README, modules/main,
	modules/module-0.scm, modules/module-1.scm, modules/module-2.scm:
	Minor cleanup.

	* README: Added intro stuff, restructured a bit.

	* box-dynamic/README, box-module/README, box/README: Cleanup and
	restructuring.

	* box-dynamic-module/box-mixed.scm: New file, demonstrating usage
	of extension library functionality, but without exporting
	procedures from the library.

	Thanks to Thomas Wawrzinek for the idea and example code!

	* box-dynamic-module/box-module.scm: Add comments, export
	make-box, box-ref, box-set!.

	* box-dynamic-module/README: Integrate new module (box-mixed),
	restructure and cleanup a bit.