Minimal changes to import IPython from IronPython

Summary:

1) IPython/core/compilerop.py: not all flags have the "compiler_flag" attribute

2) IPython/core/completer.py: __main__ is undefined

3) IPython/core/prompts.py: os.getuid() is not defined

4) IPython/lib/inputhook.py: ctypes SystemError

5) IPython/utils/process.py and IPython/utils/_process_cli.py: adds a new _process_cli.py which would handle the processes under cli.

6) IPython/utils/io.py: opened devnull in append mode