Modified CLI parsing API.

[Ori Bernstein <ori@xxxxxxxxxxxxxx>]

I'm moving away from getopt-like strings, and towards something that specifies
arguments so that help messages can be automatically generated. For an example
of usage, take a look at the mbld source:

	http://git.eigenstate.org/ori/mc.git/tree/mbld/main.myr

To see the data structures and implementation:

	http://git.eigenstate.org/ori/mc.git/tree/libstd/optparse.myr

Eventually, when I fix environment capture, I may move to closures for parsed
options, rather than argument lists.

Relevant summary:

	opts = [        
		/* only used for the description: usage: progname [arg summary] argdesc */
		.argdesc = "inputlist description",

		/* if we get less than minargs [discounting options], we error */
		.minargs = 1

		/* 
			the description of the option list.

			-h and -? are handled automatically, but you can
			override if you want.
		*/
		.opts = [
			/* an option that takes a mandatory argument */
			[.opt='x', .arg="xample", .desc="description"],
			/* an option that takes an optional argument: -*/
			[.opt='o', .arg="optional", .desc="description", .optional=true],

			/* an option that takes no argument. */
			[.opt='y', .arg="", .desc="description"],
			/* equivalently, .arg= can be dropped */
			[.opt='z', .desc="description"],
		][:]
	]

	parsed = std.optparse(args, &opts)
	for o in parsed.opts
		match o
		| ('x', arg):	/* arg is a string */
		| ('y', arg):	/* arg is an empty string for no args. */
		| ('y', ""):	/* again, empty string; since 'z' takes no
				   args, we always get an empty value */
		| ('z', ""):	/* see above */
		| _:
			/* due to exhaustiveness checking, we have to have
			a default case. */
			std.die("impossible");
		;;
	;;

	for a in parsed.args:
		std.put("arg: %s\n", arg)
	;;


-- 
    Ori Bernstein