Add a custom Body:setMass function.

src/modules/physics/box2d/Body.h

@@ -242,6 +242,12 @@ namespace box2d
 		**/
 		void setMassData(float x, float y, float m, float i);
 
+		/**
+		* Sets just the mass. This is provided as a LOVE bonus. Lovely!
+		* @param m The mass.
+		**/
+		void setMass(float m);
+
 		/**
 		* Sets the inertia while keeping the other properties
 		* (mass and local center).