and get a very obvious speedup in performance. This adds a configurable
'interval' to the dragpan control (and an interval to the 'drag' control,
defaulting to 0px). Patch put together by tcoulter. (Closes#1509)
git-svn-id: http://svn.openlayers.org/trunk/openlayers@7608 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf