1. Remove connection type header files and put prototypes locally and in
glcd-drivers.h. Don't fall into the pitfall of too many header files again.
2. Create a separate frame buffer structure (this allows easier re-use of
the frame buffer functions).
3. Add a function to retrieve pixel values from framebuffer.
4. Add the 'serdisplib' connection type.
5. Support display width that are not a multiple of 8 (e.g. 122x32).
