Add separate overmap font, Fix framebuffer artifacts

Adds support for a separate, different-sized ASCII font for the overmap.
Now almost all map/terrain display in the game can be decoupled from the text, allowing to use readable rectangular fonts for one, and pretty square fonts for the other.

In the making of this feature, my previous attempt at fixing the framebuffer artifacts as reported in #9348 was broken on the overmap, and as a result it was folded into this feature as well, as it depends on some of the new window IDs.
The WINDOW struct from catacurse.h is only used in builds without ncurse. With ncurses, the WINDOW struct that ncurses supplies is used instead. And as far as I know the content of that struct is not public, you're supposed to use the ncurses functions with a pointer to those windows.