cffi v1.17.1

• Fix failing distutils.msvc9compiler imports under Windows (#118).
• ffibuilder.emit_python_code() and ffibuiler.emit_c_code() accept file-like objects (#115).
• ffiplatform calls are bypassed by ffibuilder.emit_python_code() and ffibuilder.emit_c_code() (#81).

Full Changelog: https://github.com/python-cffi/cffi/compare/v1.17.0...v1.17.1