Improvement: switch render start to separate interrupt.

The final design should use one interrupt for line handling/hsync hook calls 
and a separate interrupt to trigger output. This would remove the delay loop 
and give back cpu time to the main application.

This would make the system more sensitive to other non TVout interrupts firing 
as the delay loop will allow for very very fast interrupts to fire without any 
adverse effects.

This would also mitigate display issues that stem from a line taking to long to 
begin(another interrupt firing/slow hsyn hook call) rendering as it would only 
effect its own line and not push into all following lines.

Original issue reported on code.google.com by mdmetzle@gmail.com on 4 Nov 2010 at 2:46

Doctor0707 / arduino-tvout

Improvement: switch render start to separate interrupt. #21