Work around explicit empty constructor of unordered_set in C++11

With GCC version (Debian 4.9.2-10) 4.9.2 we get the following error
when compiling with -std=c++11 (default for dune 2.4):

converting to ‘const std::unordered_set<std::basic_string<char> >’ from initializer list would use explicit constructor

opm/autodiff/ParallelDebugOutput.hpp

@@ -543,7 +543,14 @@ namespace Opm
                                            Opm::UgGridHelpers::beginFaceCentroids( globalGrid ),
                                            permeability_,
                                            dynamic_list_econ_limited,
-                                           false);
+                                           false
+                                           // We need to pass the optionaly arguments
+                                           // as we get the following error otherwise
+                                           // with c++ (Debian 4.9.2-10) 4.9.2 and -std=c++11
+                                           // converting to ‘const std::unordered_set<std::basic_string<char> >’ from initializer list would use explicit constructor
+                                           , std::vector<double>(),
+                                           std::unordered_set<std::string>()
+                                           );
 
                 const Wells* wells = wells_manager.c_wells();
                 globalWellState_.init(wells, *globalReservoirState_, globalWellState_ );

opm/autodiff/SimulatorFullyImplicitBlackoilMultiSegment_impl.hpp

@@ -108,7 +108,13 @@ namespace Opm
                                        Opm::UgGridHelpers::beginFaceCentroids(grid_),
                                        props_.permeability(),
                                        dynamic_list_econ_limited,
-                                       is_parallel_run_);
+                                       is_parallel_run_,
+                                       // We need to pass the optionaly arguments
+                                       // as we get the following error otherwise
+                                       // with c++ (Debian 4.9.2-10) 4.9.2 and -std=c++11
+                                       // converting to ‘const std::unordered_set<std::basic_string<char> >’ from initializer list would use explicit constructor
+                                       std::vector<double>(), // null well_potentials
+                                       Base::defunct_well_names_);
             const Wells* wells = wells_manager.c_wells();
             WellState well_state;
             // well_state.init(wells, state, prev_well_state);

opm/autodiff/SimulatorFullyImplicitBlackoilOutput.hpp

@@ -397,7 +397,14 @@ namespace Opm
                                   Opm::UgGridHelpers::cell2Faces(grid),
                                   Opm::UgGridHelpers::beginFaceCentroids(grid),
                                   permeability,
-                                  dummy_list_econ_limited);
+                                  dummy_list_econ_limited
+                                  // We need to pass the optionaly arguments
+                                  // as we get the following error otherwise
+                                  // with c++ (Debian 4.9.2-10) 4.9.2 and -std=c++11
+                                  // converting to ‘const std::unordered_set<std::basic_string<char> >’ from initializer list would use explicit constructo
+                                  , false,
+                                  std::vector<double>(),
+                                  std::unordered_set<std::string>());
 
         const Wells* wells = wellsmanager.c_wells();
         wellstate.resize(wells, simulatorstate); //Resize for restart step

tests/test_multisegmentwells.cpp

@@ -28,6 +28,7 @@
 #define BOOST_TEST_MODULE MultisegmentWellsTest
 
 #include <vector>
+#include <unordered_set>
 #include <memory>
 #include <array>
 
@@ -106,7 +107,13 @@ struct SetupMSW {
                                         Opm::UgGridHelpers::beginFaceCentroids(grid),
                                         fluidprops->permeability(),
                                         dummy_dynamic_list,
-                                        false);
+                                        false
+                                        // We need to pass the optionaly arguments
+                                        // as we get the following error otherwise
+                                        // with c++ (Debian 4.9.2-10) 4.9.2 and -std=c++11
+                                        // converting to ‘const std::unordered_set<std::basic_string<char> >’ from initializer list would use explicit constructor
+                                        , std::vector<double>(), // null well_potentials
+                                        std::unordered_set<std::string>());
 
         const Wells* wells = wells_manager.c_wells();
         const auto wells_ecl = ecl_state->getSchedule()->getWells(current_timestep);