TODO list:

Critical:

- add structure assign.
- fix 'char' and 'short' casts.
- 0 is pointer - fix type compare
- fix L'' and L"" wide chars
- add message if external function or variable not found.
- function pointers to forward reference (patch code generator).
- add float/double support (should be as small as possible while being
  usable for RISC code generator too).

Not critical:

- fix preprocessor symbol redefinition 
- better constant opt (&&, ||, ?:)
- add ELF executable and shared library output option (would be needed
  for completness!).
- add PowerPC code generator.
- add portable byte code generator and interpreter for other
  unsupported architectures.