converted frometext* to use gettoken()
	converted:
		result = foo();
		if (result != DNS_R_SUCCESS)
			return (result);
	to
		RETERR(foo());

	Initial (committed) implementation of red/black tree of trees.

Makefile.in:
	add redblack.o to libdns.

	dns_rdataclass_fromtext() and dns_rdataclass_totext().

	txt_fromwire() was not coping with a zero length active buffer.

the Right Way.

	totext/fromtext should all work
	towire/fromwire mostly work
	tostruct/fromstruct return DNS_R_NOTIMPLEMENTED
	compare untested