added code directory, Makefile needs some work and needs to be adapted for use
with OSX and linux.

Changes to be committed:
      new file:   .gitignore
      new file:   code/Makefile
      new file:   code/blink.c
      new file:   code/include/.bits.h.swp
      new file:   code/include/bits.h
      new file:   code/include/bool.h
      new file:   code/include/iocompat.h
      new file:   code/include/num.h
      modified:   sim/psu/interface.log
      modified:   sim/psu/interface.op.raw
      modified:   sim/psu/interface.raw