Math expression applet

[Andrew Coles]

> Oh, if anyone wants a look the code is available at:
>
> http://cis.strath.ac.uk/~ac/math.tar.bz2

I've updated it a bit now - the parser supports some extra functions
(changes also applied to the original parser in kmplot) and it displays
error messages if the entered expression is invalid.  Any comments as to
where it should go would be greatly appreciated :-)

Andrew