Here is a new version with pending issues addressed.

- No abort any more.  Now, any failure marks the font as not usable,
   falling back to previous driver.  If the error is general, then all
   of DirectWrite is disabled.  eassert and DebPrint are called in these
   cases.
- Added a NEWS entry.
- The struct uniscribe_font_info is now in w32font.h
- Build without warnings in both versions on MinGW.

Some things I think we didn't discuss before:

- DirectWrite is available since Windows 7, but color glyphs are
   available only since Windows 8.1.  We only enable DirectWrite since
   Windows 8.1. This is stated on the NEWS entry.
- The default value for the Gamma render parameter in DirectWrite
   gives very 'light' characters.  I changed it to 1.4, which matches
   GDI and looks better. But that's just my opinion.

I couldn't find any hebrew font with color glyphs to test RTL
display. I found a latin+arabic one, Cairo Play:

https://github.com/Gue3bara/Cairo
https://fonts.google.com/specimen/Cairo+Play

It displays diacritics in different colors on both scripts.

It seems to work fine in emacs. I attach captures with and without
DirectWrite, and compared to Courier New.