change HDMI to fb1
always use /dev/fb0
limare: add DRM backend and decouple FB logic from core

This is only compile-tested at the moment. Also the code
relies on a custom ioctl in the exynos DRM.
limare: some fixes to the DRM backend
limare: some cleanups to the DRM backend
drm-backend: convert error messages to go to stderr
limare: handle error code from wsys open
drm-backend: fix parameter ordering
drm-backend: maybe fix the bpp selection
drm-backend: make the allocation step more verbose

Should be fine since allocation is only done once.
Plus, we currently allocate only two pages (double buffering).
drm-backend: use the term 'connector index'

The index is _not_ the ID, which is an internal identifier
chosen by the DRM.
drm-backend: more bpp fixes
fb-backend: inform user when external map fails
limare: add some debug code to fb and drm backend
drm-backend: add more error checking (page index related)
limare: handle dual buffer internally in the backend
drm-backend: add dmabuf support
drm-backend: make some functions static
drm-backend: use dmabuf instead of the GEM_PHYS ioctl hack
drm-backend: properly initialize request structs