client: fix memory leak in create_proxies

Currently, all clients will leak memory whenever events are queued and a new id is found. The create_proxies function allocates memory to a wl_proxy and casts it into a wl_object, but its memory is never freed. The approach here is to simply add a wl_proxy *new_proxy to the wl_display struct, assign the created proxy to that struct, and then free the memory when wl_display_disconnect is called.

Signed-off-by: Joe Green random342@airmail.cc