[eigen] binder1st and binder2nd

[Mathieu Dutour <mathieu.dutour@xxxxxxxxx>]

Dear all,

in its latest version, Eigen is still using std::binder1st and std::binder2nd.

As indicated in http://en.cppreference.com/w/cpp/utility/functional/binder12

those functions are deprecated since C++11 and will disappear in C++17.

Rationale for doing so is given in binders.h of gcc 5.1.0:

   *  These functions are deprecated in C++11 and can be replaced by

   *  @c std::bind (or @c std::tr1::bind) which is more powerful and flexible,

   *  supporting functions with any number of arguments.  Uses of @c bind1st

   *  can be replaced by @c std::bind(f, x, std::placeholders::_1) and

   *  @c bind2nd by @c std::bind(f, std::placeholders::_1, x).

Sincerely,

  Mathieu