Add long lines admonition

[SVN r30618]

more/discussion_policy.htm

@@ -97,6 +97,15 @@ If you use tabs to indent your source code, convert them to spaces
 before inserting the code in a posting.  Something in the processing
 chain usually strips all the indentation and leaves a mess behind.
 
+<p><a name="longlines"></a>
+
+<h3>Limit Line Length</h3>
+
+If you put source code in your postings and your mailer wraps long
+lines automatically, either keep the code narrow or insert the code as
+an (inline, if possible) attachment.  That will help ensure others can
+read what you've posted.
+
 <p><a name="quoting"></a>
 
 <h3>Don't Overquote</h3>