Properly build with the new weston build system.

Sometime soon, I need to make this *not* depend on weston.
surface: Add a destroy signal
pixman-renderer: Remove unneeded call to wlb_output_recompute_surface_position
output: Add a mode_changed signal
surface: Actually initialize the destroy signal
Remove the old fullscreen shell implementation
output: Fix and rename the surface commit listener
output: Remove the present_surface mechanism and replace with the simpler set_surface mechanism
Add a version 4 wl_fullscreen_shell implementation