Markup nit: OK and ERR should be marked \constant in running text.

Doc/lib/libcurses.tex

@@ -1028,13 +1028,12 @@ The \module{curses} module defines the following data members:
 
 \begin{datadesc}{ERR}
 Some curses routines  that  return  an integer, such as 
-\function{getch()}, return ERR upon failure.  
+\function{getch()}, return \constant{ERR} upon failure.  
 \end{datadesc}
 
 \begin{datadesc}{OK}
 Some curses routines  that  return  an integer, such as 
-\function{napms()}, return OK upon success.  
-
+\function{napms()}, return \constant{OK} upon success.  
 \end{datadesc}
 
 \begin{datadesc}{version}