[support] overriding a theme's css

[Marty Landman]

I've upgraded a D5 website for a client and the CSS files for 
nice_menus had been customized within the nice_menus module's 
directory, which obviously got overwritten by my upgrade.

Which I understand is why this wasn't the right way to do things. I'm 
sure that copying the old css files fixes the problems, because I 
did. Want to do things according to best practice. I could just take 
those entire css file contents and append them to the style.css file 
for the theme. That'd work I think, but is there a better way, w/o 
actually picking all the lines apart to see what's needed?

Marty