Colour Index Latency Correction with bitmap_addr

[WillGreen]

We use bitmap_addr to calculate the memory address from drawing coordinates. Address calculation requires three cycles, so we delay write enable (we) to match. We need to delay the colour index (cidx) similarly.

Current examples use a single colour for a shape, and the initialisation steps hide this issue. However, this bug is evident when a shape is drawn with multiple colours.

[WillGreen]

The Sinescroll demo doesn't suffer from this issue and provides a template for a fix. See code under: // delay pixel colour to match address calculation