Reverse code to avoid SDCC bug.

Once again, SDCC doesn't know how to insert elements in a linked list.
Document future plans about this project...
Fixup compiler flags.

- Make char default to unsigned to make cursor keys work.
- Remove useless duplicate define.
Fix include mixup.

Do things in the right order to make sure the keycode defines are set
the same way for everyone.
Make everything in the DSCs const

* This is the only way I found to have SDCC generate data that doens't
need a runtime init.
Don't use the generic relocator code for DSCs.

The structure is simple enough and is fixed, so a specific code can be
used. This saves a few bytes off each DSC file.