Removed an unneeded and potentially numerical instability

inducing std::abs call.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402393

dlib/svm/kcentroid.h

@@ -286,7 +286,7 @@ namespace dlib
 
                 // if this new vector isn't approximately linearly dependent on the vectors
                 // in our dictionary.
-                if (std::abs(delta) > my_tolerance)
+                if (delta > my_tolerance)
                 {
                     if (dictionary.size() >= my_max_dictionary_size)
                     {

dlib/svm/krls.h

@@ -120,7 +120,7 @@ namespace dlib
 
                 // if this new vector isn't approximately linearly dependent on the vectors
                 // in our dictionary.
-                if (std::abs(delta) > my_tolerance)
+                if (delta > my_tolerance)
                 {
                     if (dictionary.size() >= my_max_dictionary_size)
                     {