Update LLHTTP and apply patch to support C++ interop

[Lukasa]

Motivation

C++ interop support in Xcode has started to dislike the header files from llhttp. While a bug has been filed upstream at nodejs/llparse#71 it doesn't seem as though there is any movement on that fix upstream. As a result, we need to apply a patch.

To keep the code maintainable, we'd like to apply that patch in an automated fashion, so we should do so by amending the "update and patch" script. Along the way, we should update LLHTTP to the latest code.

Modifications

The modifications are split into separate commits.

1. Modify the script to fix some bugs that have crept in.
2. Run the script to update LLHTTP to latest, without the patch.
3. Fix up the tests to account for the fact that we get some different errors from LLHTTP now.
4. Apply the patch suggested by @postmechanical in Cxx interop problem #3093
5. Re-run the script, which only applies the patch

Result

C++ interop should be working again. Resolves #3093.

[adam-fowler]

@Lukasa did you remove the workaround implemented for #2274 given there was a fix upstream in LLHTTP

[Lukasa]

No I didn't. Good catch though, we should remove that workaround. I think it can be a separate patch though.