Remove overload for staticSize

This fails to compile if you cannot instanciate the default
constructor T.

The problem showed up with a std::tuple<T> where T is
not default constructible. This is a really nasty issue:
std::tuple<T> implements a default constructor but
instanciating this fails in this case.

As a consequence std::is_constructible<std::tuple<T>> is
true, but trying to instanciate it gives a compile error.
Similar behaviour can be observed with operator<.
At least for the default constructor of std::tuple
this seems to be fixed in C++17 by removing it from the
overload set if you can't instanciate one for T.

dune/solvers/common/algorithm.hh

@@ -188,14 +188,6 @@ constexpr auto staticSize(const T*, const PriorityTag<0>&)
   return {};
 }
 
-// Try if class has constexpr default constructor and size method
-template<class T>
-constexpr auto staticSize(const T*, const PriorityTag<1>&)
-  -> decltype(std::integral_constant<std::size_t,T().size()>())
-{
-  return {};
-}
-
 // Try if tuple_size is implemented for class
 template<class T>
 constexpr auto staticSize(const T*, const PriorityTag<2>&)