Update docs for change to UTF-8 by default, and emphasise UTF-8 more generally.

[originally from svn r9846]

doc/config.but

@@ -1254,12 +1254,16 @@ mechanism for PuTTY and the server to communicate this information,
 so it must usually be manually configured.
 
 There are a lot of character sets to choose from. The \q{Remote
-character set} option lets you select one. By default PuTTY will
-attempt to choose a character set that is right for your \i{locale} as
-reported by Windows; if it gets it wrong, you can select a different
-one using this control.
+character set} option lets you select one.
 
-A few notable character sets are:
+By default PuTTY will use the \i{UTF-8} encoding of \i{Unicode}, which
+can represent pretty much any character; data coming from the server
+is interpreted as UTF-8, and keystrokes are sent UTF-8 encoded. This
+is what most modern distributions of Linux will expect by default.
+However, if this is wrong for your server, you can select a different
+character set using this control.
+
+A few other notable character sets are:
 
 \b The \i{ISO-8859} series are all standard character sets that include
 various accented characters appropriate for different sets of
@@ -1273,12 +1277,6 @@ Euro symbol.
 \b If you want the old IBM PC character set with block graphics and
 line-drawing characters, you can select \q{\i{CP437}}.
 
-\b PuTTY also supports \i{Unicode} mode, in which the data coming from
-the server is interpreted as being in the \i{UTF-8} encoding of Unicode,
-and keystrokes are sent UTF-8 encoded. 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 \i{code page} which is not listed in
 the drop-down list, such as code page 866, then you can try entering
 its name manually (\c{\i{CP866}} for example) in the list box. If the