FT_Add_Module() and related functions

[Alexei Podtelezhnikov]

Hi David,

I actually thought about FT_Add_Module as a visionary interface for
dynamically plugging alternative renderers:

https://github.com/raphlinus/font-rs
https://github.com/mooman219/fontdue
https://github.com/servo/pathfinder

Admittedly, none of those projects explored this possibility or there
are more straightforward ways to achieve this.

Then there is this whole discussion on how to integrate SVG, which
again comes down to using an alternative renderer module and whether
it is worth hooking inside a single module or Add/Remove multiple
modules.
https://lists.nongnu.org/archive/html/freetype-devel/2019-07/msg00058.html

So I know that nobody uses FT_Add_Module but it is not a bad interface.

Alexei