minor fix to tips.txi

[Muthiah Annamalai]

It just fixes the mistake in comments '##' description.
-Muthu

Index: doc/interpreter/tips.txi
===================================================================
RCS file: /cvs/octave/doc/interpreter/tips.txi,v
retrieving revision 1.14
diff -u -p -r1.14 tips.txi
--- doc/interpreter/tips.txi    31 Oct 2007 01:08:15 -0000    1.14
+++ doc/interpreter/tips.txi    3 Jan 2008 19:00:47 -0000
@@ -150,7 +150,7 @@ command automatically inserts such a @sa
 aligns such a comment if it is already present.
 
 @item ##
-Comments that start with two semicolons, @samp{##}, should be aligned to
+Comments that start with double sharp-sign, @samp{##}, should be aligned to
 the same level of indentation as the code.  Such comments usually
 describe the purpose of the following lines or the state of the program
 at that point.