fix some masochistic compiler warnings for the GCC 9 pre-release

the flags which I used are
```
-pedantic \
-Wall \
-Wextra \
-Wformat-nonliteral \
-Wcast-align
-Wpointer-arith \
-Wmissing-declarations \
-Wcast-qual \
-Wshadow
-Wwrite-strings \
-Wchar-subscripts \
-Wredundant-decls \
-fstrict-overflow \
-O3 \
-march=native \
-DNDEBUG=1
```

note that some heavy filtering is not the worst idea because DUNE is
far from not emiting any warnings with these flags.

Also, there were some pesky warnings in test_ecl_output which I don't
know how to fix:

```
tests/test_ecl_output.cc:218:73: warning: missing initializer for member ‘Opm::data::Connection::effective_Kh’ [-Wmissing-field-initializers]
```

ebos/eclbaseaquifermodel.hh

@@ -86,10 +86,10 @@ public:
      * \brief Add the water which enters or leaves the reservoir due to aquifiers.
      */
     template <class Context>
-    void addToSource(RateVector& rate,
+    void addToSource(RateVector& rate OPM_UNUSED,
-                     const Context& context,
+                     const Context& context OPM_UNUSED,
-                     unsigned spaceIdx,
+                     unsigned spaceIdx OPM_UNUSED,
-                     unsigned timeIdx) const
+                     unsigned timeIdx OPM_UNUSED) const
     { }
 
     /*!
@@ -122,7 +122,7 @@ public:
      *        format.
      */
     template <class Restarter>
-    void serialize(Restarter& res)
+    void serialize(Restarter& res OPM_UNUSED)
     { }
 
     /*!
@@ -130,7 +130,7 @@ public:
      *        format.
      */
     template <class Restarter>
-    void deserialize(Restarter& res)
+    void deserialize(Restarter& res OPM_UNUSED)
     { }
 
 protected:

ebos/eclequilinitializer.hh

@@ -107,7 +107,6 @@ public:
 
         unsigned numElems = vanguard.grid().size(0);
         unsigned numCartesianElems = vanguard.cartesianSize();
-        typedef typename GET_PROP_TYPE(TypeTag, FluidSystem) FluidSystem;
 
         EQUIL::DeckDependent::InitialStateComputer<TypeTag> initialState(materialLawManager,
                                                                          eclState,

ebos/eclwellmanager.hh

@@ -101,7 +101,7 @@ public:
      *
      * I.e., well positions, names etc...
      */
-    void init(const Opm::EclipseState& eclState,
+    void init(const Opm::EclipseState& eclState OPM_UNUSED,
               const Opm::Schedule& deckSchedule)
     {
         // create the wells which intersect with the current process' grid
@@ -609,7 +609,7 @@ public:
     }
 
 protected:
-    bool wellTopologyChanged_(const Opm::EclipseState& eclState,
+    bool wellTopologyChanged_(const Opm::EclipseState& eclState OPM_UNUSED,
                               const Opm::Schedule& schedule,
                               unsigned reportStepIdx) const
     {

ebos/eclwriter.hh

@@ -384,7 +384,6 @@ private:
         }
 
         const auto& globalGridView = globalGrid_.leafGridView();
-        typedef typename Grid::LeafGridView GridView;
 #if DUNE_VERSION_NEWER(DUNE_GRID, 2,6)
         typedef Dune::MultipleCodimMultipleGeomTypeMapper<GridView> ElementMapper;
         ElementMapper globalElemMapper(globalGridView, Dune::mcmgElementLayout());
@@ -450,7 +449,6 @@ private:
         int ny = eclState().getInputGrid().getNY();
 
         const auto& globalGridView = globalGrid_.leafGridView();
-        typedef typename Grid::LeafGridView GridView;
 #if DUNE_VERSION_NEWER(DUNE_GRID, 2,6)
         typedef Dune::MultipleCodimMultipleGeomTypeMapper<GridView> ElementMapper;
         ElementMapper globalElemMapper(globalGridView, Dune::mcmgElementLayout());

ebos/equil/initstateequil.hh

@@ -713,9 +713,9 @@ phaseSaturations(const Grid& grid,
                                          /*storeSaturation=*/true,
                                          /*storeDensity=*/false,
                                          /*storeViscosity=*/false,
-                                         /*storeEnthalpy=*/false> SatOnlyFluidState;
+                                         /*storeEnthalpy=*/false> MySatOnlyFluidState;
 
-    SatOnlyFluidState fluidState;
+    MySatOnlyFluidState fluidState;
     typedef typename MaterialLawManager::MaterialLaw MaterialLaw;
 
     const bool water = FluidSystem::phaseIsActive(FluidSystem::waterPhaseIdx);
@@ -1129,7 +1129,7 @@ private:
     }
 
     template <class RMap, class MaterialLawManager>
-    void calcPressSatRsRv(const Opm::EclipseState& eclState,
+    void calcPressSatRsRv(const Opm::EclipseState& eclState OPM_UNUSED,
                           const RMap& reg,
                           const std::vector< Opm::EquilRecord >& rec,
                           MaterialLawManager& materialLawManager,