+clarify what attach_charset does, see http://bugs.mutt.org/3165
+and http://bugs.debian.org/502628
+
+--- a/init.h
++++ b/init.h
+@@ -197,7 +197,10 @@
+ /*
+ ** .pp
+ ** This variable is a colon-separated list of character encoding
+- ** schemes for text file attachments.
++ ** schemes for text file attachments. Mutt uses this setting to guess
++ ** which encoding files being attached are encoded in to convert them to
++ ** a proper character set given in $$send_charset.
++ ** .pp
+ ** If \fIunset\fP, the value of $$charset will be used instead.
+ ** For example, the following configuration would work for Japanese
+ ** text handling: