fix crash calling nonexistent delegate (also memory leak)

VDKQueue.h

@@ -29,6 +29,7 @@
 //
 //      VDKQueue is also simplified. The option to use it as a singleton is removed. You simply alloc/init an instance and add paths you want to
 //      watch. Your objects can be alerted to changes either by notifications or by a delegate method (or both). See below. 
+//      When you're done with the object, call stopWatching (to release the background thread), then release.
 //
 //      It also fixes several bugs. For one, it won't crash if it can't create a file descriptor to a file you ask it to watch. (By default, an OS X process can only
 //      have about 3,000 file descriptors open at once. If you hit that limit, UKKQueue will crash. VDKQueue will not.)
@@ -139,6 +140,7 @@ extern NSString * VDKQueueAccessRevocationNotification;
 - (void) removePath:(NSString *)aPath;
 - (void) removeAllPaths;
 
+- (void) stopWatching;                                              // You must call this when you release the VDKQueue object
 
 - (NSUInteger) numberOfWatchedPaths;                                //  Returns the number of paths that this VDKQueue instance is actively watching.
 

VDKQueue.m

@@ -141,12 +141,6 @@ - (id) init
 
 - (void) dealloc
 {
-    // Shut down the thread that's scanning for kQueue events
-    _keepWatcherThreadRunning = NO;
-
-    // Do this to close all the open file descriptors for files we're watching
-    [self removeAllPaths];
-
     [_watchedPathEntries release];
     _watchedPathEntries = nil;
 
@@ -422,6 +416,22 @@ - (void) removeAllPaths
 }
 
 
+- (void) stopWatching
+{
+    // This method must be called if we want this object to ever be dealloc'd. This is because detachNewThreadSelector:toTarget:withObject:
+    // retains the target (in this case, self), setting the retainCount to 2. Aside from the memory leak issue, if the thread is never terminated,
+    // the watcher thread might still try to send messages to a nonexistent delegate, causing your app to crash.
+    @synchronized(self)
+    {
+        // Shut down the thread that's scanning for kQueue events
+        _keepWatcherThreadRunning = NO;
+
+        // Do this to close all the open file descriptors for files we're watching
+        [_watchedPathEntries removeAllObjects];
+    }
+}
+
+
 - (NSUInteger) numberOfWatchedPaths
 {
     NSUInteger count;