Add support for parse_translation_unit2 api.

[cfis]

No description provided.

[ioquatix]

Would it make sense to add a comment explaining why it exists, what problem it solves over the non-2 version?

[cfis]

clang_parseTranslationUnit2 returns an error code indicating what went wrong. In addition, if you look at Clang's documentation, it focuses on clang_parseTranslationUnit2 - see https://clang.llvm.org/doxygen/group__CINDEX__TRANSLATION__UNIT.html#ga494de0e725c5ae40cbdea5fa6081027d.

The docs for clang_parseTranslationUnit are limited, only saying "Same as clang_parseTranslationUnit2, but returns the CXTranslationUnit instead of an error code. In case of an error this routine returns a NULL CXTranslationUnit, without further detailed error codes." See https://clang.llvm.org/doxygen/group__CINDEX__TRANSLATION__UNIT.html#ga2baf83f8c3299788234c8bce55e4472e

Thus my conclusion is use clang_parseTranslationUnit2 in favor of clang_parseTranslationUnit.

[ioquatix]

Is there any point to continue providing the original API?

[cfis]

No, but I didn't want to be removing existing methods. I'll leave the decision to you.

[cfis]

I updated the PR to have parse_translation_unit be a alias to parse_translation_unit2. I did leave in the FFI definition though.

[ioquatix]

What do you think about dropping the alias and 2 suffix? I don’t think this will be a big compatibility issue.

[cfis]

That's a good idea. Done.