Optimizations for better usage of XS code

xs/src/Line.cpp

@@ -36,6 +36,12 @@ Line::length() const
     return this->a.distance_to(&(this->b));
 }
 
+Point*
+Line::midpoint() const
+{
+    return new Point ((this->a.x + this->b.x) / 2.0, (this->a.y + this->b.y) / 2.0);
+}
+
 void
 Line::from_SV(SV* line_sv)
 {