[dev] PATCH add mouseover colors to Mnemo.

[Chuck Hagenbuch]

Quoting mike@graftonhall.co.nz:

> If someone can come up with a better alorgithm for choosing calculations
> a mouseover color then feel free, this is the best i can come up with at
> the moment. It just lightens the color, kinda need to do the opposite if 
> it's a really light color...

Committed, thanks. I turned down the factor of brightening, though, since I 
was getting highlight colors that were indistinguishable from each other...

-chuck

--
Charles Hagenbuch, <chuck@horde.org>
"After a few minutes the most aromatic and nice smelling Italian coffee 
 will come out of the exhaustpipe." - Our stove-top espresso pot