The testcase was disabled but seems to be working.

Signed-off-by: Alexander Hansen <[email protected]>

The frame pointer could have been changed by the function that was
called. Since it is using YL:YH also for it's frame pointer.

So the frame pointer needs to be restored after a call.

This example is for the atmega328p.

It's showing how to transmit increasing numbers and how to configure the
USART peripheral.

It's been tested with logic analyzer and USART protocol decoder but not
yet connected to an actual USART receiver / usb to serial converter.

This incomplete implementation just looks if the temporary
for the value being returned is wide.

It can be completed by also checking the with of the type of the value being returned.

This needs to be expanded further and put into all LOAD/STORE
IR instructions.

create a redzone in memory to detect unintended writes around the target
address.

new wrapper function to simplify reading a value from 2 adjacent
registers.

also test 16 bit values for TAC_STORE_CONST_ADDR

test 16 bit values for TAC_LOAD_CONST_ADDR