WIP font stuff for ImGui

[db48x]

Summary

Interface "use Freetype to render fonts for ImGui, and use multiple fonts in the ImGui interface"

Purpose of change

Make ImGui use Roboto by default, and the Freetype rasterizer. Load both the configured gui font and the normal monospaced font for use by ImGui. Make item descriptions use the mono font for drawing ASCII artwork. Configure hinting so that Terminus and unifont don’t look awful.

Fixes #76420

Testing

Check out the artwork for a pistol or something.

Additional context

This is a draft for a reason: I need someone who builds on Windows and/or Mac to give me the right CFLAGS/LDFLAGS for linking against Freetype2

[harakka]

Is there a particular reason for adding a new font to the mix, and are there any issues with including Apache licensed material in a cc-by-sa 3.0 project?

[db48x]

Good questions. Yes, the reason for adding Roboto is that it is a proportional font. We could pick from quite a selection, but Roboto was ready to hand, appropriately licensed, inoffensively styled (not deliberately weird or thematic, or deliberately bad like Comic Sans, etc), and has relatively thick strokes even at small font sizes (which makes it render well even if we stick to the default STB rasterizer which cannot do any hinting). And of course the user can override the choice if they prefer something else.

Apache 2.0 is completely compatible with the Creative Commons license, and it meets the definition of an Open Source license.

[db48x]

I guess it builds fine on OSX. Anyone want to give it a try and make sure it works?