Added a missing const. Its absence was causing a compile time error.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403761

dlib/svm/krr_trainer.h

@@ -64,7 +64,7 @@ namespace dlib
         }
 
         bool will_estimate_lambda_for_regression (
-        )
+        ) const
         {
             return use_regression_loss;
         }

dlib/svm/krr_trainer_abstract.h

@@ -181,7 +181,7 @@ namespace dlib
         !*/
 
         bool will_estimate_lambda_for_regression (
-        );
+        ) const;
         /*!
             ensures
                 - returns true if the automatic lambda estimation will attempt to estimate a lambda