Add files for general graphic buffer
Add basic buffer datatype
Add basic buffer initialisation
Add query functions
Add begin_access() and end_access()
Merge pull request #134 from neithernut/add-compositor-buffer

Add buffer type
Moved the framebuffer population to the monitor

This commit moves the populate_framebuffers to the monitor internals.
This was planned from the start and thus the code did not really change and
only the return values had to be changed.