Bugfix of bottom bridges. If close regions shall be closed by bridges,

these regions are grown to anchor the bridge lines to the bottom surface.
The grown regions may overlap. In that case the regions are now merged
before the bridging direction is calculated for the merged region.

xs/src/libslic3r/BoundingBox.hpp

@@ -32,6 +32,8 @@ class BoundingBoxBase
     void translate(coordf_t x, coordf_t y);
     void offset(coordf_t delta);
     PointClass center() const;
+    bool contains(const PointClass &point) const;
+    bool overlap(const BoundingBoxBase<PointClass> &other) const;
 };
 
 template <class PointClass>