ivi-shell: add shell surface labels
ivi-shell: add shell surface labels

To be used by the Weston timeline feature for identifying surfaces in a
trace. The 'get_label' functionality can also be used by any debugging
code, too.

Signed-off-by: Pekka Paalanen <0f6ae7001e34c37b02fb2c1c2573ddf8f442136a@collabora.co.uk>
Reviewed-by: Eugen Friedrich <d4422ed1e14343198966fa0f35c3c77077052941@gmail.com>

giucam/weston,giucam/weston,Gnurou/weston,krezovic/weston,krezovic/weston,sir-murray/weston,sir-murray/weston,Gnurou/weston