message: Fix to persistence landscapes. Hopefully it will now compile on osx and Marc's computer
diff: @@ -48,6 +48,10 @@ namespace Gudhi_stat
  +//predeclaration
  +class Persistence_landscape;
  +template < typename operation >
  +Persistence_landscape operation_on_pair_of_landscapes( const Persistence_landscape& land1 , const Persistence_landscape& land2 );
  @@ -126,10 +130,10 @@ public:
  **/
  friend std::ostream& operator<<(std::ostream& out, Persistence_landscape& land );
  + template < typename operation >
  + friend Persistence_landscape operation_on_pair_of_landscapes( const Persistence_landscape& land1 , const Persistence_landscape& land2 );
  +
  -protected:
  - template < typename oper > friend Persistence_landscape operation_on_pair_of_landscapes ( const Persistence_landscape& land1 , const Persistence_landscape& land2 );
  -public:
  /**
  