Removal of unprefixed container_of()

[Chad Versace]

wayland-util.h defines __wl_container_of() as well as an unprefixed version,
container_of(). The unprefixed version, of course, pollutes the global namespace
and causes symbol collisions in projects that define container_of() slightly
differently.

Is there any chance that the unprefixed container_of() macro in wayland-util.h
can be renamed or removed before the 1.0 freeze?

I'll write the patch if the wayland dev's are ok with its removal.

-Chad