fix some issues introduce by virtualizing this function

you cannot mix virtual and overloads with a default parameter
making the methods indistinguishable.

Apps/Common/SIMCoupled.h

@@ -53,7 +53,13 @@ public:
   }
 
   //! \brief Computes the solution for the current time step.
-  virtual bool solveStep(TimeStep& tp, bool firstS1 = true)
+  virtual bool solveStep(TimeStep& tp)
+  {
+    return this->solveStep(tp, true);
+  }
+
+  //! \brief Computes the solution for the current time step.
+  virtual bool solveStep(TimeStep& tp, bool firstS1)
   {
     if (firstS1)
       return S1.solveStep(tp) && S2.solveStep(tp);

Apps/Common/SIMCoupledSI.h

@@ -32,7 +32,8 @@ public:
   virtual ~SIMCoupledSI() {}
 
   //! \brief Computes the solution for the current time step.
-  virtual bool solveStep(TimeStep& tp, bool firstS1 = true)
+  using SIMCoupled<T1,T2>::solveStep;
+  virtual bool solveStep(TimeStep& tp, bool firstS1)
   {
     if (maxIter <= 0)
       maxIter = std::min(this->S1.getMaxit(),this->S2.getMaxit());

Apps/Common/SIMSolverTS.h

@@ -128,11 +128,10 @@ public:
             return 2;
       }
     }
-
-    return 0;
   }
 
 protected:
+  using SIMSolver<T1>::parse;
   //! \brief Parses a data section from an XML element.
   virtual bool parse(const TiXmlElement* elem)
   {