Fix copyf() in set for next version of libreset

The next version uses `void*` instead of `void const*` as
return/argument type.
Merge pull request #150 from matthiasbeyer/fix-for_next_libreset

Fix copyf() in set for next version of libreset
Add ws_wayland_obj_set_resource()
Add ws_wayland_buffer_set_resource()
Add files for implementation of wl_surface
Add preliminary initial implementation of wl_surface
Add initial surface interface definition (stubs)
Add initialisation of underlying wayland resource
Add destruction of waysome side object
Add image buffer member
Add preliminary attach callback implementation