message: elle.printf: Handle `void const*`.
diff: @@ -144,6 +144,16 @@ namespace elle
  fmt % "nullptr";
  }
  + inline
  + void
  + feed(boost::format& fmt, void const* value)
  + {
  + if (value)
  + fmt % value;
  + else
  + fmt % "nullptr";
  + }
  +
  template <typename T>
  void
  feed(boost::format& fmt, T* value)
  