message: Add missing inequality test for crypto::signature
diff: @@ -45,6 +45,10 @@ namespace fc { namespace crypto {
  return eq_comparator<signature::storage_type>::apply(p1._storage, p2._storage);
  }
  + bool operator != ( const signature& p1, const signature& p2) {
  + return !eq_comparator<signature::storage_type>::apply(p1._storage, p2._storage);
  + }
  +
  bool operator < ( const signature& p1, const signature& p2)
  {
  return less_comparator<signature::storage_type>::apply(p1._storage, p2._storage);
  