Largely converted assembler to fixed with integers, added machine header

  - Assembler now also uses fixed width integers
  - Added machine shared header with fixed integer datatypes
  - Modified code to not assume size of fixed integers
    -> Object file format could, for instace, be easily converted
       from 16 bit to 32 bit (for future use)
Added data section to object file format

  - Assembler directive '.dat' starts data section
  - Linker honors file format and concatenates data sections independend
    of code section and aranges result data section after result code
    section
  - Linker relocates addresses correctly (depending whether they point
    to data or code)