Added a missing &

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402832

dlib/matrix/matrix_utilities.h

@@ -500,7 +500,7 @@ namespace dlib
             matrix<T,N,N,MM1,L1>& a,
             matrix<long,N,NX,MM2,L2>& indx,
             T& d,
-            matrix<T,N,NX,MM3,L3> vv
+            matrix<T,N,NX,MM3,L3>& vv
         )
         /*!
             ( this function is derived from the one in numerical recipes in C chapter 2.3)