Cleanup test code and fixed compiler warning.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403068

dlib/svm/kernel.h

@@ -392,7 +392,7 @@ namespace dlib
 
         kernel_derivative(const linear_kernel<T>& k_) : k(k_){}
 
-        const sample_type& operator() (const sample_type& x, const sample_type& y) const
+        const sample_type& operator() (const sample_type& x, const sample_type& ) const
         {
             return x;
         }

dlib/test/svm.cpp

@@ -420,7 +420,7 @@ namespace
         obj.x = x;
         obj.k = k;
         kernel_derivative<kernel_type> der(obj.k);
-        DLIB_CASSERT(dlib::equal(derivative(obj)(y) , der(obj.x,y), 1e-5), "");
+        DLIB_TEST(dlib::equal(derivative(obj)(y) , der(obj.x,y), 1e-5));
     }
 
     void test_kernel_derivative (