We are not going to use them, at least in the foreseeable future

Also, uncomment code again, just "if (0)" it out, so it doesn't get stale again.

We should hang those off somewhere else. For now, the unused ones can go.

For run-time checking.

Also makes hb-ot-shape call morx for now instead of GSUB... Just for testing.

Untested, but compiles.

Also makes hb-view to use 8 bits of subpixel precision and shape at
requested size, instead of always shaping at upem and scaling results.

Like hb-view, but prints out buffer contents.

The output format is kinda cryptic.  Suggestions welcome.

Now we can use the same code to do other utils...

We now support using -1 for NUL-terminated strings.

Can be -1 for NUL-terminated string.  This is useful for passing parts
of a larger string to a function without having to copy or modify the
string first.

Affected functions:

	hb_tag_t hb_tag_from_string()
	hb_direction_from_string()
	hb_language_from_string()
	hb_script_from_string()

For two reasons:

1. User can always call hb_buffer_pre_allocate() themselves, and

2. Now we do a pre_alloc in add_utfX anyway, so the total number of
reallocs is limited to a small number (~3) anyway.  This just makes the
API cleaner.