[cadcdev-tiki] time-based Drawables

[Sam S. <sam...@gm...>]

The nextFrame function in the Drawable class takes a uint64 tm.  
Should this be the relative time since the last frame, or the  
absolute time since the menu started?

Tiki's built-in visualPerFrame is always passing this as zero, but  
I've modified my copy to pass the time since the last frame instead.   
Any objections to committing this?

-Sam