made spec more clear

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402369

dlib/optimization/optimization_abstract.h

@@ -168,7 +168,7 @@ namespace dlib
             - is_matrix<T>::value == true (i.e. T must be a dlib::matrix type)
             - x.nc() == 1 (i.e. x must be a column vector)
         ensures
-            - Performs an unconstrained minimization of the function f() using a 
+            - Performs an unconstrained minimization of the function f() using the BFGS 
               quasi newton method.  The optimization stops when any of the following
               conditions are satisfied: 
                 - the change in f() from one iteration to the next is less than min_delta