Ensures that vertical sync and end-of-visible-lines conditions potentially trigger whenever line_counter_ changes, not only when it increments.
Ensures that vertical sync and end-of-visible-lines conditions potentially trigger whenever line_counter_ changes, not only when it increments.

TomHarte/CLK,TomHarte/CLK,TomHarte/CLK,TomHarte/CLK,TomHarte/CLK