Eliminate redundant timestep class

Since all construction should go through the wrapper method, and the
class otherwise just handed everything down to the base class, we might
as well inline everything in there to avoid someone starting to make
their own objects of this type.

opm/core/io/eclipse/EclipseWriter.cpp

@@ -551,18 +551,10 @@ struct EclipseSummary : public EclipseHandle <ecl_sum_type> {
 private:
     vars_t vars_;
 
-    /// Make sure a new timestep is flushed to the summary section
-    struct EclipseTimeStep : public EclipseHandle <ecl_sum_tstep_type> {
-        EclipseTimeStep (const EclipseSummary& sum,
-                         const SimulatorTimer& timer)
-            : EclipseHandle <ecl_sum_tstep_type> (
-                  ecl_sum_add_tstep (sum,
-                                     timer.currentStepNum (),
-                                     // currentTime is always relative to start
-                                     Opm::unit::convert::to (timer.currentTime (),
-                                                             Opm::unit::day)),
-                  ecl_sum_tstep_free) { }
-    };
+    // don't define a new type for timesteps (since they should all
+    // be created with makeTimeStep anyway), just use the basic handle
+    // type and a typedef.
+    typedef EclipseHandle <ecl_sum_tstep_type> EclipseTimeStep;
 
     // hold memory for each timestep alive until we can flush it;
     // each time step is temporarily referenced in writeTimeStep,
@@ -574,7 +566,13 @@ private:
     /// method instead of creating your own timestep objects, as it
     /// will make sure that the
     std::shared_ptr <EclipseTimeStep> makeTimeStep (const SimulatorTimer& timer) {
-        auto tstep = std::make_shared <EclipseTimeStep> (*this, timer);
+        auto tstep = std::make_shared <EclipseTimeStep> (
+                    ecl_sum_add_tstep (*this,
+                                       timer.currentStepNum (),
+                                       // currentTime is always relative to start
+                                       Opm::unit::convert::to (timer.currentTime (),
+                                                               Opm::unit::day)),
+                    ecl_sum_tstep_free);
         steps_.push_front (tstep);
         return tstep;
     }
@@ -600,6 +598,9 @@ private:
     }
 };
 
+// in order to get RTTI for this "class" (which is just a typedef), we must
+// ask the compiler to explicitly instantiate it.
+template struct EclipseHandle<ecl_sum_tstep_struct>;
 
 /**
  * Summary variable that reports a characteristics of a well.