Apple has both an Empty and Null constants. Our implementation is largely
done in managed code and, for historical reasons [1], match System.Drawing
behaviour. Still the constant is useful for other (e.g. 3rd party) APIs.
Also add CFRect.Infinite for the missing CGRectInfinite symbol.
[1] In the original classic we only provided RectangleF not CGRect
references:
* https://bugzilla.xamarin.com/show_bug.cgi?id=43628
* xtro
common.unclassified:!missing-field! CGRectNull not bound
common.unclassified:!missing-field! CGRectInfinite not bound
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