split string to avoid buffer overflow in native english speaking persons (fix suggested by The Wanderer)

Originally committed as revision 4447 to svn://svn.ffmpeg.org/ffmpeg/trunk

doc/ffmpeg-doc.texi

@@ -1156,8 +1156,8 @@ First, (@pxref{Coding Rules}) above if you didn't yet.
 When you submit your patch, try to send a unified diff (diff '-up'
 option). I cannot read other diffs :-)
 
-Also please do not submit patches which contain several unrelated changes,
-split them into individual self-contained patches, this makes reviewing 
+Also please do not submit patches which contain several unrelated changes.
+Split them into individual self-contained patches; this makes reviewing 
 them much easier.
 
 Run the regression tests before submitting a patch so that you can