Merge some BS1.7 changes:

Boolean operation feature

src/slic3r/GUI/Gizmos/GLGizmosManager.hpp

@@ -70,6 +70,7 @@ public:
         Scale,
         Flatten,
         Cut,
+        MeshBoolean,
         FdmSupports,
         Seam,
         // BBS
@@ -327,7 +328,7 @@ private:
     bool grabber_contains_mouse() const;
 };
 
-
+std::string get_name_from_gizmo_etype(GLGizmosManager::EType type);
 
 } // namespace GUI
 } // namespace Slic3r