better wording for the alphabetical lists

Originally committed as revision 8918 to svn://svn.ffmpeg.org/ffmpeg/trunk

doc/ffmpeg-doc.texi

@@ -1717,8 +1717,8 @@ do not attach several unrelated patches to the same mail.
     If you added a new file, did you insert a license header? It should be
     taken from FFmpeg, not randomly copied and pasted from somewhere else.
 @item
-    Longer lists of things are usually kept in alphabetical order. If you
-    add an item, make sure to maintain alphabetical order.
+    You should maintain alphabetical order in alphabetically ordered lists as
+    long as doing so does not break API/ABI compatibility.
 @item
     Did you provide a suggestion for a clear commit log message?
 @end enumerate