Also, include hb-dsalgs.hh from end of hb-pricate.hh

Oops.

Catches compile-errors in them better.

gen-def.py: pass headers as arguments so that msys2 can convert posix paths

let python's parse command-line args as usual

When one is not using the msys2 python, the header files that are passed in as environment
variable cannot be found.

https://ci.appveyor.com/project/fonttools/ttfautohint-py/build/1.0.65/job/rkremny4jjid9nl2#L803

This is because msys2 shell and make use POSIX paths (e.g. /c/Users/clupo/...)
whereas non-msys2 python.exe uses native Windows paths (e.g. C:\Users\clupo\...).

Msys2 will automatically convert command line arguments (but not environment variables) from
POSIX to Windows paths when calling a native win32 executable, so we pass the header paths
as arguments instead of environment variables.

This way the gen-def.py script can support both mingw python running in an MSYS2 shell, and
native win32 python.

Fixes #481

Completes #1037 and fixes #1035.

Disable vectorization for now.  To correctly use them, we should
use posix_memalign() to allocate them.  Otherwise, can cause
misaligned access.

https://bugs.chromium.org/p/chromium/issues/detail?id=860184

../../src/hb-ot-layout-gsubgpos-private.hh:391:18: warning: missed loop optimization, the loop counter may overflow [-Wunsafe-loop-optimizations]

From the new code (first paragraph is from the OT Devanagari spec.):

  /*   o Reorder matras:
   *
   *     If a pre-base matra character had been reordered before applying basic
   *     features, the glyph can be moved closer to the main consonant based on
   *     whether half-forms had been formed. Actual position for the matra is
   *     defined as “after last standalone halant glyph, after initial matra
   *     position and before the main consonant”. If ZWJ or ZWNJ follow this
   *     halant, position is moved after it.
   *
   * IMPLEMENTATION NOTES:
   *
   * It looks like the last sentence is wrong.  Testing, with Windows 7 Uniscribe
   * and Devanagari shows that the behavior is best described as:
   *
   * "If ZWJ follows this halant, matra is NOT repositioned after this halant.
   *  If ZWNJ follows this halant, position is moved after it."
   *
   * Test case, with Adobe Devanagari or Nirmala UI:
   *
   *   U+091F,U+094D,U+200C,U+092F,U+093F
   *   (Matra moves to the middle, after ZWNJ.)
   *
   *   U+091F,U+094D,U+200D,U+092F,U+093F
   *   (Matra does NOT move, stays to the left.)

Fixes https://github.com/harfbuzz/harfbuzz/issues/1070

Test case added with Adobe Devanagari.

The get_table imple was wrong, as table offsets in a dfont are
relative to the resource.  We were treating them as relative to
the big blob itself.  To be fixed.

Part of https://github.com/harfbuzz/harfbuzz/pull/1085

In collaboration with Behdad

From the issue:
"In this font, the virama,ya first forms a ligature, then decomposes back to
virama,ya. This causes those two to be marked parts of a MultipleSubst
sequence. When attaching the matra, we look for the first of the MultipleSubst
sequence because that's where we attach to (because of eg #740). In this case,
the first glyph in the MultipleSubst sequence is a mark, so we skip it and
attach to the base char before it."

Font in question is Nirmala UI from Windows 10. Test sequence:

  U+0926,U+094D,U+092F,U+0941

Fixes https://github.com/harfbuzz/harfbuzz/issues/1020

Fixes https://github.com/harfbuzz/harfbuzz/issues/1073

Indic shaper already had this check.  We removed it when forking
Khmer shaper by mistake.

Fixes https://bugzilla.mozilla.org/show_bug.cgi?id=1464623

Fixes #1081

Oops

* Handle EINTR on fallback reader
* Increase fallback reader limitation size limitation to 2 << 28
* Ensure _O_BINARY does exist if MMAP is used on Windows
  (maybe superfluous but makes me more confident)

Makes compiling without HAVE_ROUND on systems that do have it work.