Randomization only happens by default. If the user specifies a value for
'rand', that value is respected.

Sorry for the noise, downstream custom builders.  Please adjust.

New API:
+hb_font_funcs_set_glyph_h_advances_func
+hb_font_funcs_set_glyph_v_advances_func
+hb_font_get_glyph_h_advances
+hb_font_get_glyph_h_advances_func_t
+hb_font_get_glyph_v_advances
+hb_font_get_glyph_v_advances_func_t

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

Ouch!

Towards possibly using Null pool for some nil objects.

Right now only Old Italic is marked as such.

Fixes https://github.com/harfbuzz/harfbuzz/issues/1000

For consistency.

New API:
HB_BUFFER_FLAG_REMOVE_DEFAULT_IGNORABLES
hb-shape / hb-view --remove-default-ignorables

One more text-rendering-tests test passing.  Eleven failing.

So I can merge this to master...

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

This only counts recursions right now.  Good start.

Hopefully...
Fixes https://github.com/behdad/harfbuzz/issues/429

This should affect mark attachment in vertical text.  I have no font to test,
but this sounds the right order.

Noticed while debugging https://github.com/behdad/harfbuzz/issues/532

Fixes tests/shaping/tests/cluster.tests

Fixes tests/automatic-fractions.tests

Makes consumption easier.