Part of https://github.com/harfbuzz/harfbuzz/issues/1652

Part of https://github.com/harfbuzz/harfbuzz/issues/1652

For some reasons djgpp doesn't understand "unsigned int" can be same
with one of uint*_t anyway so lets do that for it explicitly.

Just to note, our CI's djgpp is based GCC 7.2.0 and isn't old.

Newer compilers / language allows structs with constructor in union.
So, this was not actually testing anything.  Indeed, the recent
change in DISALLOW_COPY *is* making some of our types non-POD.
That broke some bots.

Just remove this since it wasn't doing much, and I'd rather have
DISALLOW_COPY.

Show up with gcc -O0.

There's a few more but those are functions that need to be filled in.

Maybe this is a lost battle...

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.

From Lorna Evans: "That was a new character added to Unicode 11.0"

See comment.

Now I wonder if any bots will be unhappy we calling | in static const initializations...
Or would that cost runtime init?  Our tests don't detect any..

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

Found and fixed a couple bugs.

Found a couple multithreading issues.  Marked them with "XXX-MT-bug".

Fixes https://github.com/harfbuzz/harfbuzz/issues/345

Previously we made CGJ unskippable.  Now, if CGJ did NOT prevent
any reordering, allow skipping over it.  To make this work we
had to make changes to the Arabic mark reordering algorithm
implementation to renumber moved MCM marks.  See comments.

Fixes https://github.com/harfbuzz/harfbuzz/issues/554

Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=4099

Part of fixing https://github.com/behdad/harfbuzz/pull/605

In ten years we never used them...

No flag is safe, over time... See previous commit.

Fixes https://github.com/behdad/harfbuzz/issues/509

Not all shapers code is updated to set this properly.
GSUB and Arabic shaper are updated.
GPOS and other shapers are NOT.

Fixes https://github.com/behdad/harfbuzz/issues/224

Fixes https://github.com/behdad/harfbuzz/issues/505

Fixes https://github.com/behdad/harfbuzz/issues/408

New approach to fix this:
https://github.com/behdad/harfbuzz/commit/69f9fbc4200442a35484d3c790ae8f4979be5d60

Previous approach was reverted as it was too broad.  See context:
https://github.com/behdad/harfbuzz/issues/347#issuecomment-267838368

With U+05E9,U+05B8,U+05C1,U+05DC and Arial Unicode, we now (correctly) disable
GDEF and GPOS, so we get results very close to Uniscribe, but slightly different
since our fallback position logic is not exactly the same:

Before:		[gid1166=3+991|gid1142=0+737|gid5798=0+1434]
After:		[gid1166=3+991|gid1142=0@402,-26+0|gid5798=0+1434]
Uniscribe:	[gid1166=3+991|gid1142=0@348,0+0|gid5798=0+1434]

Fixes https://github.com/behdad/harfbuzz/issues/234