bug#73730: 31.0.50; Support for color fonts on MS-Windows

[Cecilio Pardo]

The attached patch works without a new font driver.

This requires the harfbuzz font backend to be available.

It works by modifying the harfbuzz backend to use DirectWrite at
some points, if it is available:

- When encoding characters: w32hb_encode_char
- When measuring text: w32font_text_extents
- When drawing text: w32font_draw

DirectWrite is setup by calling w32_initialize_direct_write.  From
that point, the function w32_use_direct_write will return true if
DirectWrite is to be used.

The lisp variable w32-inhibit-direct-write can switches it on and off.

It builds with Mingw64 and Mingw. As mingw doesn't have the DirectWrite 
includes, I had to declare a lot of things at the start of the file. 
This line marks the end of that:

/* End of dwrite_3.h definitions.  */

I have tested this only on Windows 11.

0001-Implement-drawing-text-with-DirectWrite-on-MS-Window.patch
Description: Text document