Changed code slightly to avoid compiler error in some versions of gcc.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402336

dlib/svm/krls.h

@@ -325,10 +325,13 @@ namespace dlib
         matrix<scalar_type,0,1,mem_manager_type> k;
         matrix<scalar_type,1,0,mem_manager_type> temp_matrix;
 
-        const static double tau = 0.01;
+        const static double tau;
 
     };
 
+    template <typename kernel_type>
+    const double krls<kernel_type>::tau = 0.01;
+
 // ----------------------------------------------------------------------------------------
 
     template <typename kernel_type>