boxes: Add function to create a rectangle from floating clutter rect

Meta rectangles are integer based while clutter works in floating coordinates,
so when converting to integers we need a strategy.

Implement the shrink strategy by ceiling the coordinates and flooring the width,
and the grow strategy reusing clutter facility for this.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/3

src/core/boxes-private.h

@@ -274,6 +274,10 @@ void meta_rectangle_transform (const MetaRectangle  *rect,
                                int                   height,
                                MetaRectangle        *dest);
 
+void meta_rectangle_from_clutter_rect (ClutterRect          *rect,
+                                       MetaRoundingStrategy  rounding_strategy,
+                                       MetaRectangle        *dest);
+
 void meta_rectangle_crop_and_scale (const MetaRectangle *rect,
                                     ClutterRect         *src_rect,
                                     int                  dst_width,