Use inttypes for stdint types

This should help make RGBDS portable to systems with 16-bit integers,
like DOS.

For kicks, use the macros for 16-bit and 8-bit integers.

Fix other miscellaneous things, like #include ordering and other
printf-format related things.

Reduce repitition in math.c while I'm there.

src/gfx/main.c

@@ -210,7 +210,7 @@ int main(int argc, char *argv[])
 
 	if (opts.trim &&
 	    opts.trim > (raw_image->width / 8) * (raw_image->height / 8) - 1) {
-		errx(1, "Trim (%i) for input raw_image file '%s' too large (max: %i)",
+		errx(1, "Trim (%d) for input raw_image file '%s' too large (max: %u)",
 		     opts.trim, opts.infile,
 		     (raw_image->width / 8) * (raw_image->height / 8) - 1);
 	}

src/gfx/makepng.c

@@ -38,7 +38,7 @@ struct RawIndexedImage *input_png_file(const struct Options *opts,
 
 	if (img.depth != depth) {
 		if (opts->verbose) {
-			warnx("Image bit depth is not %i (is %i).",
+			warnx("Image bit depth is not %d (is %d).",
 			      depth, img.depth);
 		}
 	}