Fixed typo in spec

--HG--
extra : convert_revision : svn%3Afdd8eb12-d10e-0410-9acb-85c331704f74/trunk%403096

dlib/stl_checked/std_vector_c_abstract.h

@@ -316,7 +316,7 @@ namespace dlib
         ); 
         /*!
             ensures
-                - size() == 0
+                - #size() == 0
         !*/
 
         reference operator[](