changes for ironpython (notebook)

- the undefined $HOME 'absurd' string is tolerable by os.path.abspath
- prevent from importing not supported modules - pyexpect, io
- spawning child python process includes extra parameter -X:Frames
- aligned execution path with windows cpython
- bytes_to_str, str_to_bytes and cast_bytes have ironpython specific
  version
- added windows specific version for confirm exit
- stubbed out not supported FunctionType ctor