scanner: Generate client stubs for wl_display requests

We used to special case this because of the untyped new-id argument in
the bind request.  Now that the scanner can handle that, we can
remove the special case.

Switching to the generated stubs does bring an API change since we now
also take the interface version that the client expects as an argument.
Previously we would take this from the interface struct, but the
application may implement a lower version than what the interface struct
provides.  To make sure we don't try to dispatch event the client
doesn't implement handlers for, we have to use a client supplied version
number.