In Layer.setVisibility, call Layer.moveTo with zoomChanged = true, so that the
grid tiles are reloaded. In an ideal world, the grid tiles would only be loaded
if they haven't been loaded yet. This would spare us the split second wait
while the browser reloads those images from the cache, but we want to release
today, so it'll have to wait.
git-svn-id: http://svn.openlayers.org/trunk/openlayers@1448 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf