Fixed invalid message in an assert statement.

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%402895

dlib/matrix/matrix_subexp.h

@@ -48,7 +48,7 @@ namespace dlib
     { 
         DLIB_ASSERT(inc > 0, 
             "\tconst matrix_exp range(start, inc, end)"
-            << "\n\tstart can't be bigger than end"
+            << "\n\tInvalid inputs to this function"
             << "\n\tstart: " << start 
             << "\n\tinc:   " << inc
             << "\n\tend:   " << end