bug#8943: octave mode: "mismatched parentheses" warning on multiline comments

[fork]

When using multiline comments in octave mode, there is a "mismatched
parentheses" warning issued to the mini-buffer when closing the comment.  

For example, the warning appears on the final "}" in the following code:

%{
blah blah blah 
%}

There doesn't seem to be any problems with indentation.  Also, I see the same
result for both "#{" and "%{"

Thanks for all your excellent work!