Revert "inherit ctor's from geometry_base"

- Fixes #3473 (windows compile)
 - TODO: @artemp get to the bottom of how to inherit from base class
   in a way that works with boost::variant and across platforms

This reverts commit bf99177da7.

include/mapnik/geometry.hpp

@@ -148,7 +148,11 @@ struct geometry : geometry_base<T>
 
     geometry()
         : geometry_base<T>() {} // empty
-    using geometry_base<T>::geometry_base;
+
+    template <typename G>
+    geometry(G && geom)
+        : geometry_base<T>(std::forward<G>(geom)) {}
+
 };
 
 template <typename T>