Generated header issue with Swift Cxx interop

Per the recommendation [here](https://github.com/apple/swift-nio/issues/3093), I am opening an issue on this repo to request a change to the generated `c_nio_llhttp.h` header. It appears that the `stdint.h` include [here](https://github.com/nodejs/llparse/blob/e2ae9d4446c58c9508a2904e45bf6b1161287131/src/compiler/header-builder.ts#L26) needs to be moved outside the `extern "C"` block and included as `<cstdint>` when Cxx interop is enabled for Swift packages that use it to both compile and not break the debugger.