fileutils_eintr.patch: handle EINTR for open, fopen and dup (only on Linux for dup in _Py_dup).

_Py_wfopen() and _Py_fopen() are not modified because callers are not really prepared to handle exceptions. These functions are mostly used during early steps of Python initializations. If someone is motived, you can propose a patch for these functions.

For other functions (cwd, readlink, etc.), it's not clear to me if we can get EINTR or not.