Fixes https://github.com/harfbuzz/harfbuzz/issues/1724

https://github.com/harfbuzz/harfbuzz/issues/1740

I guess all of its field will be initialized anyway here but lets make it more defensive

Causing -Wextra-semi-stmt build error when no primitive has chosen
Interesting that nobody has noticed it yet.

mingw.org's MinGW.

src/hb-algs.hh: Don't compile _BitScanForward and _BitScanReverse
for GCC >= 4.  mingw.org's MinGW doesn't have these functions.

src/hb-atomic.hh: MemoryBarrier does exist in mingw.org's MinGW,
but it is not a macro, it is an inline function.  __MINGW32_VERSION
is a macro that exists only in mingw.org's MinGW, so conditioning
on it should not affect MinGW64, where MemoryBarrier is a macro.

src/hb-uniscribe.cc: Define E_NOT_SUFFICIENT_BUFFER if it is not
defined (mingw.org's MinGW doesn't).

src/hb.hh: Don't include intrin.h for mingw.org's MinGW, since that
header is not available; instead, include windows.h.  Conditioned
on __MINGW32_VERSION to avoid affecting MinGW64.

Saves a few bytes.

Don't use vsnprintf when HB_NO_BUFFER_MESSAGE is defined

Sometime between [July 2018] and [January 2019], the OpenType Myanmar
grammar changed: one asat is now allowed after a medial ya, before any
other medial consonant.

[July 2018]: http://web.archive.org/web/20180711011550/https://docs.microsoft.com/en-us/typography/script-development/myanmar
[January 2019]: http://web.archive.org/web/20190115044451/https://docs.microsoft.com/en-us/typography/script-development/myanmar

This also reverts commit 439b0586, which
allowed an asat immediately after a medial ra.

fixed faulty FDSelect::sanitize

Originally introduced in 21ede867 (#1314) but as it wasn't applied to hb_bsearch
accidentally removed while merging hb_bsearch_r to it.

It should've done in a branch

A part of #593

Hopefully autotools timestamps issues will go

Based on https://github.com/harfbuzz/harfbuzz/issues/1730#issuecomment-497151210

That one doesn't even understand constexpr.

https://github.com/harfbuzz/harfbuzz/issues/1730

https://github.com/harfbuzz/harfbuzz/issues/1730

Hopefully fixes https://github.com/harfbuzz/harfbuzz/issues/1730

https://github.com/harfbuzz/harfbuzz/issues/1730