[Open-graphics] Clock generation

[James Richard Tyrer]

It appears that the solution to the jitter problem might be to change 
the way that we generate the clocks.

Something like this could be used to generate the existing two clocks 
plus a third one to drive the pixel clock generators:

http://focus.ti.com/lit/ds/symlink/cdcel937.pdf

This is EEPROM (1K cycles) so it can't be used for the pixel clock 
generators.

For the pixel clock generators, the maximum frequency required and 
output voltage required are going to be the main parameters to choose parts.

-- 
JRT