(OSX) Add preliminary drag and drop code

ui/drivers/cocoa/cocoa_common.m

@@ -64,6 +64,7 @@ void *glkitview_init(void);
    
 #if defined(HAVE_COCOA)
    [self setAutoresizingMask:NSViewWidthSizable | NSViewHeightSizable];
+    [self registerForDraggedTypes:[NSArray arrayWithObjects:NSColorPboardType, NSFilenamesPboardType, nil]];
 #elif defined(HAVE_COCOATOUCH)
    self.view = (__bridge GLKView*)glkitview_init();
    
@@ -96,6 +97,41 @@ void *glkitview_init(void);
 {
 }
 
+- (NSDragOperation)draggingEntered:(id <NSDraggingInfo>)sender
+{
+    NSDragOperation sourceDragMask = [sender draggingSourceOperationMask];
+    NSPasteboard *pboard = [sender draggingPasteboard];
+    
+    if ( [[pboard types] containsObject:NSFilenamesPboardType] )
+    {
+        if (sourceDragMask & NSDragOperationCopy)
+            return NSDragOperationCopy;
+    }
+    
+    return NSDragOperationNone;
+}
+
+- (BOOL)performDragOperation:(id<NSDraggingInfo>)sender
+{
+    NSPasteboard *pboard = [sender draggingPasteboard];
+    
+    if ( [[pboard types] containsObject:NSURLPboardType])
+    {
+        NSURL *fileURL = [NSURL URLFromPasteboard:pboard];
+        NSString *s = [fileURL path];
+        if (s != nil)
+        {
+           RARCH_LOG("Drop name is: %s\n", [s UTF8String]);
+        }
+    }
+    return YES;
+}
+
+- (void)draggingExited:(id <NSDraggingInfo>)sender
+{
+    [self setNeedsDisplay: YES];
+}
+
 #elif defined(HAVE_COCOATOUCH)
 - (void)viewDidAppear:(BOOL)animated
 {