server: dbg message

print when we are trying to overwrite surface
server: add support for multiple surfaces

Since client can ask for more than one surface, store them into list
client: replace dispatch_pending with roundtrip

Dispatch pending didn't worked all the time. This is more robust (but
slower).
server: add implementation of wl_surface's destroy method
server: remove resource when destroying sufrace

It's not needed anymore
global: add SEND_BYTES operation implementation

add general SEND_BYTS operation
core: add SEND_BYTES operation implementation

This allows client to send bytes to the display. Display accepts the
data usign wit_display_process_request()
seat: save seat's name into seat's data

when we get seat's name method, save the name into data of seat object
tests: add test for send_bytes