[pypy-issue] Issue #1980: None in a rffi.llexternal call become /* nothing */ after translation (pypy/pypy)

[mattip]

New issue 1980: None in a rffi.llexternal call become /* nothing */ after translation
https://bitbucket.org/pypy/pypy/issue/1980/none-in-a-rffillexternal-call-become

mattip:

Using a None in a RPython rffi.llexternal function call results in ```/*nothing*/``` when translated.

Can we get either an error earlier in the translation process or a NULL emitted in code, rather than a crash of c-compilation?
```ztranslation``` passed in this case

[Here](https://gist.github.com/mattip/93f22744ad9384f48596) is an example of a complete translated function, from stdlib-2.7.9 pypy/module/_ssl/interp_win32.py