An Xy right after a gradient mesh's /End X! is the mesh's only when the
mesh's own 6 () XW follows. When the layer's LB follows (directly or
after the layer's Xd and 7 () XW) it is the layer's, as before, and the
mesh keeps the state it had. Also corrects the revision-history row that
still said meshes with handle weights of 0 aren't read.