winemac: Prevent interpolation of the window surface image when it's blitted to the actual window.

On high-resolution Retina displays, the OS X window backing store has twice the
pixels as Wine's window backing store.  So, our images get scaled up.  Core
Graphics had been interpolating/smoothing the image, which resulted in
fuzziness.  This tells it not to do that.

I had assumed this wouldn't be necessary since we pass FALSE for the
shouldInterpolate parameter of CGImageCreate() when we create the images.
Apparently, that's not sufficient.

dlls/winemac.drv/cocoa_window.m

@@ -265,6 +265,7 @@ - (void) drawRect:(NSRect)rect
 
                 context = (CGContextRef)[[NSGraphicsContext currentContext] graphicsPort];
                 CGContextSetBlendMode(context, kCGBlendModeCopy);
+                CGContextSetInterpolationQuality(context, kCGInterpolationNone);
 
                 for (i = 0; i < count; i++)
                 {