Clarify what happens when you enter a code page that's not listed.

[originally from svn r3467]

doc/config.but

@@ -1,4 +1,4 @@
-\versionid $Id: config.but,v 1.68 2003/09/25 12:38:02 jacob Exp $
+\versionid $Id: config.but,v 1.69 2003/09/26 13:04:56 jacob Exp $
 
 \C{config} Configuring PuTTY
 
@@ -1091,9 +1091,10 @@ If you select \q{UTF-8} as a character set you can use this mode.
 Not all server-side applications will support it.
 
 If you need support for a numeric code page which is not listed in
-the drop-down list, such as code page 866, then you should be able
-to enter its name manually (\c{CP866} for example) in the list box
-and get the right result.
+the drop-down list, such as code page 866, then you can try entering
+its name manually (\c{CP866} for example) in the list box. If the
+underlying version of Windows has the appropriate translation table
+installed, PuTTY will use it.
 
 \S{config-cyr} \q{Caps Lock acts as Cyrillic switch}