MksScreenAttributes is an opaque type with setters so that we can
potentially extend it in the future without ABI issues.
Furthermore, this adds a configure API for both sync and async to
MksScreen.
Currently, I get NOT_SUPPORTED back from Qemu, but I think that's because
I'm not even past the bootloader/EFI stage for tests.
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.
