protocol: Add release requests for wl_pointer, wl_keyboard, and wl_touch

We missed destroy requests in the 1.0 protocol and since the scanner
generates local-only *_destroy requests in that case we can't add
destroy requests without breaking protocol.  A client needs to verify
that the server provides a version 3 seat to use the protocol destructor
so the name needs to be something else than wl_*_destroy.

v2 (Rob Bradford): Rebased, bumped the protocol versions and added since
attributes to the requests.