* hb_ot_color_has_svg
* hb_ot_color_glyph_svg_create_blob

Barely made a dent :(.

Fixes https://github.com/harfbuzz/harfbuzz/pull/1317
Fixes https://oss-fuzz.com/v2/testcase-detail/6543700493598720

Towards https://github.com/harfbuzz/harfbuzz/pull/1317

https://github.com/harfbuzz/harfbuzz/pull/1317

We were returning the accelerator's lookup count.  Returns table's.
They are the same except for OOM cases.  Just shorter code.

Preparation for fixing https://github.com/harfbuzz/harfbuzz/pull/1317

Closer to what CoreText does.

Fixes https://github.com/harfbuzz/harfbuzz/issues/1302

https://github.com/harfbuzz/harfbuzz/issues/1302

Add pointer cast operator and plus operator.

Follow up on 94e421ab

If we have duplicae font files in different directories, that would
break the oss-fuzz build currently.  So, rename some to avoid
name class with text-rendering-test.  Would be better to find
another solution.

From bungeman.

Fixes https://github.com/harfbuzz/harfbuzz/pull/1314

When hb_set_t::page_for_insert needs to insert at the end of the page_map
it ends up evaluating '&page_map[i + 1]' which has hb_vector return an
lvalue of a Crap so that nothing can be moved to its address. This turns
into issues with ThreadSanitizer on Crap when two threads modify different
hb_set_t instances. This can be avoided by using '&page_map[i] + 1'
instead.

They are so slow and we had only a couple of Cygwin build failure
reported in ~5 years.

https://github.com/harfbuzz/harfbuzz/pull/1309#issuecomment-432778270

One of the was missed before.  Not intentional.

Looks like AppVeyor has new enough packages for our needs. Cuts CI build
time by 5 minutes.

Some fonts, like msmincho, have positive number as descent
in vhea table.  That's wrong.  Just enforce sign on ascent/descent
when reading both horizontal and vertical metrics.

Fixes https://github.com/harfbuzz/harfbuzz/issues/1248

Only merge when actual ligature happened.

Fixes https://github.com/harfbuzz/harfbuzz/issues/1305

Only works at entire-buffer range, not sub-ranges.

Test with:

$ hb-shape Zapfino.dfont Zapfino
[Z_a_p_f_i_n_o=0+2333]

$ hb-shape Zapfino.dfont Zapfino --features=-dlig
[Z=0+416|a=1@-21,0+264|p_f=2+433|i=4+181|n=5+261|o=6+250]

$ hb-shape Zapfino.dfont Zapfino --features=+dlig
[Z_a_p_f_i_n_o=0+2333]

Fixes https://github.com/harfbuzz/harfbuzz/issues/1303