shell: Add missing cases to switch statements for surface types
shell: Add missing cases to switch statements for surface types

This fixes a load of GCC warnings when compiling with -Wswitch-enum
-Wswitch-default, and makes it clearer that those cases have been
thought about explicitly when writing the code, rather than just being
forgotten.

xorgy/weston,giucam/weston,mchalupa/weston,Tarnyko/weston-xdg_surface_present,mchalupa/weston,eyolfson/weston,udoprog/weston,krezovic/weston,giucam/weston,eyolfson/weston,Fantu/compositor-spice,Tarnyko/weston-xdg_surface_present,jonnylamb/weston,jonnylamb/weston,Gnurou/weston,sir-murray/weston,xorgy/weston,krezovic/weston,Fantu/compositor-spice,sir-murray/weston,Gnurou/weston,kwm81/weston,Fantu/compositor-spice,udoprog/weston,kwm81/weston