New graphics card(s): Quadram Quadcolor I / I+II

[roybaer]

This adds support for the Quadram Quadcolor I graphics card and its daughter board, the Quadcolor II.

The Quadcolor I by itself expands CGA memory to 32 KiB, adds a background color setting for the high resolution CGA mode and can switch between two ROM fonts.
The Quadcolor II adds a separate 64 KiB linear framebuffer for a 640x200x16 mode similar to that of the Tandy Graphics Adapter II. The pixel data from both framebuffers is ORed together.

Note that I neither have the original hardware nor relevant old software for testing.
This implementation follows the technical documentation of the card(s), but only the Quadcolor II mode has been tested, and only with my own code, namely a code path in https://github.com/planet-x3/px3_ose/tree/obscure-hw.