o Added a cancelAllDownloads stub to the tile sources

@@ -92,6 +92,10 @@
                                  userInfo:nil];
 }    
 
+- (void)cancelAllDownloads
+{
+}
+
 - (RMFractalTileProjection *)mercatorToTileProjection
 {
     if (!tileProjection) {

@@ -1106,6 +1106,7 @@
     if (tileSource == newTileSource)
         return;
 
+    [tileSource cancelAllDownloads];
     [tileSource autorelease];
     tileSource = [newTileSource retain];
 

@@ -41,6 +41,7 @@
 @protocol RMTileSource <NSObject>
 
 - (UIImage *)imageForTile:(RMTile)tile inCache:(RMTileCache *)tileCache;
+- (void)cancelAllDownloads;
 
 - (RMFractalTileProjection *)mercatorToTileProjection;
 - (RMProjection *)projection;