Fallthrough in usage should be break

[BenBE]

While looking through my local changes I noticed a small difference between the local changes and the upstream develop branch:

heatshrink/src/heatshrink.c

Lines 410 to 412 in ffd9505

	case 'h': /* help */
	usage();
	/* FALLTHROUGH */

In my local version I imported the fix for #46 using a break in that place, which is IMHO the more natural choice, as you normally don't expect the usage() display to cause any side-effects on your program configuration, thus resulting in the following code locally instead:

        case 'h':               /* help */
            usage();
            break;

Given that usage() internally calls exit(1); this is even stranger, as this comment causes the expectation of the code continuing after the call to usage(); returns.