Make TypedefElaborated respect @add_def

[melonedo]

Fix #320

[Gnimuc]

This line can be removed as well.

[Gnimuc]

The @add_def macro was originally designed for adding identifiers in the system headers. After adding multi-platform support, this macro is mainly for skipping something wrong or unexpected. As a result, the current implementation is a mess and needs to be refactored in the future.

[melonedo]

This line can be removed as well.

Is this because currently tags are not translated?

[Gnimuc]

As mentioned above, initially @add_def was for adding identifiers in the system headers, at that time, all the system-header definitions need to be manually wrapped.

Then, when implementing the multi-platform support, @add_def was for extracting specific identifiers in the system headers, for example, @add_def tm can be used to tell the generator to search tm in the system headers and generate a wrapper for tm. This was still very cumbersome because users need to add those @add_defs manually.

Then, the experimental CollectDependentSystemNode pass was added, so all dependent system nodes can be automatically handled. So, @add_def is now only for doing workaround.

This PR adds || haskey(dag.ids_extra, leaf_ty.sym)) for TypedefElaborated to make the behavior consistent with TypedefDefault, which is mainly for fixing the old behavior for extracting typedef identifiers in the system headers.
However, this line was for rewriting the definition of tm to a custom one, which turns out to be a misuse now.

The @add_def macro has two different meanings for typedef-ed identifiers and tag types. It needs to be separated into two macros, one for extracting identifiers @extract_def and one for skipping tag types @skip_def. But it's not trivial to do the refactor.

[melonedo]

I added a test case for this.

[melonedo]

The tests failures are with Julia 1.7. New CI scripts is not enabled.

[Gnimuc]

need to rebase this PR onto master.

[melonedo]

Oops this keeps having conflicts as new tests are added.