'struct glcd_framebuf' now contains a layout type which can either be
FB_TYPE_LINEAR (this is the default) or FB_TYPE_VPAGED. This actually affects
the drawing function and the frame-buffer memory calculation. A new 'size'
field is added to store the pre-calculated length.
Adopt existing driver to make use of the new feature (currently only glcd2usb
driver).
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).
image writer is for debugging only. The Freetype font renderer still misses
some features (e.g. big numbers, character encoding, non-standard cell size).
mmdolze