(Mode Line): Clarify that coding systems are characters, not letters.

Fixes: debbugs:1749

doc/emacs/ChangeLog

 2011-07-10  Lars Magne Ingebrigtsen  <larsi@gnus.org>
 
+	* screen.texi (Mode Line): Clarify that coding systems are
+	characters, not letters (bug#1749).
+
 	* cmdargs.texi (Environment): Mention removing variables
 	(bug#1615).  Text suggested by Kevin Rodgers.
 

doc/emacs/screen.texi

@@ -190,7 +190,7 @@ sometimes useful to have this information.
 Systems}).  If it is a dash (@samp{-}), that indicates the default
 state of affairs: no special character set handling, except for the
 end-of-line translations described in the next paragraph.  @samp{=}
-means no conversion whatsoever.  Letters represent various nontrivial
+means no conversion whatsoever.  Characters represent various nontrivial
 @dfn{coding systems}---for example, @samp{1} represents ISO Latin-1.
 On a text-only terminal, @var{cs} is preceded by two additional
 characters that describe the coding system for keyboard input and the