Commit a number of improvements to grid handling from #449. This adds

support for buffer:0 on grids, and includes changes to Remove extra 
rows and columns from the grid in _initTiles when reusing an existing 
grid, which is a fix to #357 and #436. 


git-svn-id: http://svn.openlayers.org/trunk/openlayers@2091 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf

lib/OpenLayers/Tile.js

@@ -69,7 +69,12 @@ OpenLayers.Tile.prototype = {
     /**
     */
     draw:function() {
-        this.drawn = true;
+        this.clear();
+        return ((this.layer.displayOutsideMaxExtent
+                || (this.layer.maxExtent
+                    && this.bounds.intersectsBounds(this.layer.maxExtent, false)))
+                && !(this.layer.buffer == 0
+                     && !this.bounds.intersectsBounds(this.layer.map.getExtent(), false)));
     },
     
     /**