That moment when you realise that even without a working kern.img, there is a
colourful square drawn on screen...

Added the tutorials gpio source file for the essential blinking lights, no
other way to debug.

First bug was with the prolog and epilog, turns out that stmfd and ldmfd is
required.

Second bug was with send_mail.  Accessing write location with non hex value,
also doing comparison with value in status field with one zero too few.

Now debugging the render functions
Solved issues.

The set_pixel func is slow - optimize that in future