- To make it easier to resolve linking problems, at the top of assembler
files always add a .module.

- to add init code; call from main or add to .area _GSINIT.

- always ensure you specify correct .area in your assembler code so that 
code and data is put in the place you want.

- Make as much as possible const static; or const at least. 
This will avoid SDCC from generating code in the GSINIT sections to 
initialise structures/variables that do not change.

- Always initialise variables; do not assume SDCC will use '0' as default 
value. Often it doesn't it uses 0x0ff instead!

- If linking against a 'kernel'; ensure kernel has as many functions as 
required. If you remove linking against z80 library, you can find library 
routines used and then you can remove them if they are not needed.
