This just starts on the DMA-BUF code and abstracts MksPaintable so it can
encapsulate both MksDmabufPaintable and MksCairoFramebuffer.
Currently, the dmabuf just tailes everything (fully) but we can fix that
with snapshot work stil. Either way, want to get the abstraction landed
first before we dive deeper into that.
This library doesn't do much yet. It contains the scaffolding and the
rough shape of what I think the API should be in mks-types.h. Some of the
types have some skeleton implementation as well to hid the D-Bus API
behind those types.
The next steps are to fill out the other wrapper objects and see what
properties we should expose from the underlying D-Bus proxies.
Along with that, will be a GtkWidget which can have a number of properties
set on it to specify the MksScreen, MksKeyboard, and MksMouse devices. It
may make sense to attach the session + screen to the widget, so that it can
adapt to keyboard and mouse changes though.
