The X server should fill in the minor version that it supports in the
case where it only supports the older version, so we can safely always
pass a higher version number than is potentially supported by the
server.
libXi was designed to be stable in the case where it doesn't recognize
requests or events/replies, so this should still work in a case where
we have new versions of the X server, and GTK+, but an old version of
libXi, at least for however well that setup should work.