wayland: Simplify slave version management

Slave objects should always be the same version as their parent
constructor, except for the generic wl_registry.bind.
wayland: Simplify global version management

libwayland-server already checks the bounds of the bind for versioning,
meaning that the value that we pass to wl_global_create is all we need.
wayland: Fix naming scheme for request handlers

Our implementations should take the name of the request.
wayland: Add a few statics we forgot before