Fixed grammar

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402655

dlib/matrix/matrix_abstract.h

@@ -447,7 +447,8 @@ namespace dlib
 
                 Also note that the elements of this matrix are contiguous in memory and 
                 stored in row major order.  Additionally, all memory allocations are
-                performed using the memory manager object supplied as template argument.
+                performed using the memory manager object supplied as a template argument
+                to this class.
         !*/
 
     public: