fix new warnings and escape apply namespace

- `std::apply` is part of C++17 and the compiler wants to use it because
of ADL. Thus it is now necessary to escape it as `::apply`.
- remove some `using namespace std` remaining in the sources.
- fix simple warnings.

eo/tutorial/Lesson5/eoOneMaxMutation.h

@@ -44,7 +44,7 @@ public:
      * modifies the parent
      * @param _genotype The parent genotype (will be modified)
      */
-    bool operator()(GenotypeT & _genotype)
+    bool operator()(GenotypeT & /*_genotype*/)
 	{
 	    bool isModified(true);
 	    // START code for mutation of the _genotype object

eo/tutorial/Lesson5/eoOneMaxQuadCrossover.h

@@ -46,7 +46,7 @@ public:
      * @param _genotype1 The first parent
      * @param _genotype2 The second parent
      */
-    bool operator()(GenotypeT& _genotype1, GenotypeT & _genotype2)
+    bool operator()(GenotypeT& /*_genotype1*/, GenotypeT & /*_genotype2*/)
 	{
 	    bool oneAtLeastIsModified(true);
 	    // START code for crossover of _genotype1 and _genotype2 objects

eo/tutorial/Lesson5/make_op_OneMax.h

@@ -73,7 +73,7 @@
 */
 
 template <class EOT>
-eoGenOp<EOT> & do_make_op(eoParameterLoader& _parser, eoState& _state, eoInit<EOT>& _init)
+eoGenOp<EOT> & do_make_op(eoParameterLoader& _parser, eoState& _state, eoInit<EOT>& /*_init*/)
 {
   // this is a temporary version, while Maarten codes the full tree-structured
   // general operator input