Added a missing typedef to the pipe object.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402971

dlib/pipe/pipe_kernel_1.h

@@ -61,6 +61,8 @@ namespace dlib
 
     public:
 
+        typedef T type;
+
         explicit pipe_kernel_1 (  
             unsigned long maximum_size
         );