Fixes test just added.

Reported by Nona while updating Android to HarfBuzz 2.0.0.

SFSNDisplay uses these.  We just apply the default kern without
variations right now.  But at least makes the default kern work.

Re https://github.com/harfbuzz/harfbuzz/issues/1271

This needs reviewing

run-shape-fuzzer-tests.py automatically runs valgrind if see available
but test/api runs it by request, we probably should normalize the approaches
later

Actually the check is right,

On -myanmar.hh, on that particular switch, OT_C is indic_category_t
but OT_D is myanmar_category_t so we are mixing the types in one variable.

And on -arabic.cc, step can goes one number higher than step_t enum in the
loop so we are actually using it as an unsinged int.

Okay, let's see if the gods are happy now...

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=11034

This reverts commit 191eef82.

Behdad apparently not interested on them

Ugly as hell, and don't even understand why some bits are needed.
But the logic is sound.

I added them but now that I think, it is a bad idea to have them as
fuzzing bots will find good seeds to tweak in order to find easy new
testcases which causes duplicated issues.

fixes #1266