Cache wayland globals
Store the wayland registry globals in a list so that we can bind to them from a user/test program. When a custom interface (protocol extension) is used in a wayland compositor, this allows user/test program to use that interface. For instance, one might provide a custom wayland test protocol that give access to otherwise hidden/missing functionality that allows effective automated testing (in wayland engines). See the Weston unit test suite for an example of this concept.
Patch by: "U. Artie Eoff" <ullysses.a.eoff@…>