fix error introduce by merge (in curve_abc constructor)

include/curves/curve_abc.h

@@ -32,11 +32,6 @@ struct  curve_abc : std::unary_function<Time, Point>,
   typedef Point_derivate   point_derivate_t;
   typedef Time    time_t;
 
-  /* Constructors - destructors */
-  public:
-    /// \brief Constructor.
-    curve_abc(){}
-
   /* Constructors - destructors */
  public:
   /// \brief Constructor.