winemac: Make WineOpenGLContext hold a strong reference to its view.

Its superclass, NSOpenGLContext, only holds a weak reference.  The view was
sometimes being deallocated before the context was disposed of, resulting in
crashes.

dlls/winemac.drv/cocoa_opengl.m

@@ -35,10 +35,26 @@ @implementation WineOpenGLContext
 
     - (void) dealloc
     {
+        [[self view] release];
         [latentView release];
         [super dealloc];
     }
 
+    - (void) setView:(NSView*)newView
+    {
+        NSView* oldView = [self view];
+        [super setView:newView];
+        [newView retain];
+        [oldView release];
+    }
+
+    - (void) clearDrawable
+    {
+        NSView* oldView = [self view];
+        [super clearDrawable];
+        [oldView release];
+    }
+
     /* On at least some versions of Mac OS X, -[NSOpenGLContext clearDrawable] has the
        undesirable side effect of ordering the view's GL surface off-screen.  This isn't
        done when just changing the context's view to a different view (which I would