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.

edo/application/cmaes/main.cpp

@@ -84,7 +84,7 @@ int main(int ac, char** av)
     eoPop< RealVec >& pop = do_make_pop(parser, state, *init);
 
     // (2) First evaluation before starting the research algorithm
-    apply(eval, pop);
+    ::apply(eval, pop);
 
     // Prepare bounder class to set bounds of sampling.
     // This is used by edoSampler.