upgrading pycparser to its latest release

[eliben]

Greetings, cffi maintainers :)

I've recently released pycparser 3.0. The major change is that it's much more lightweight - without carrying a vendored PLY dependency. All functionality remains the same, and it's about 30% faster

I tried testing CFFI with the latest pycparser release, and the only failures were in a couple of places in testing/cffi0/test_parsing.py where the tests expect a very precise formatting of the error raised by pycparser on invalid code. The text of the raised error is now different, so a few tests failed - but this is very easy to fix.

FYI if you'd like to release a new version of CFFI at some point (which - I assume - will pick up the latest pycparser, because the dependency isn't version-locked in your pyproject.toml file).

All the best

[eliben]

I went ahead and created PR #224 to address the test failures.