Previously all card-specific stuff was scattered across xserver.nix
and opengl.nix, which is ugly. Now it can be kept together in a single
card-specific module. This required the addition of a few internal
options:
- services.xserver.drivers: A list of { name, driverName, modules,
libPath } sets.
- hardware.opengl.package: The OpenGL implementation. Note that there
can be only one OpenGL implementation at a time in a system
configuration (i.e. no dynamic detection).
- hardware.opengl.package32: The 32-bit OpenGL implementation.
