lib/parser: Separate Markdown code from reStructuredText

[wenzeslaus]

This restores the original 'rest' file for reStructuredText output so that it is in a separate function (and file) from Markdown. The reStructuredText output is removed from the Markdown code. While this currently introduces some duplication, it allows for further modifications of Markdown without a need to modify the reStructuredText at the same time. Even now, there are significant differences between the outputs due to the differences in syntax (headings, images, command line option lists). Anyway, the reStructuredText is scheduled for removal since the initial addition of the Markdown build, so a separate file will be easy to remove later (and this is basically a first step in the removal).

[wenzeslaus]

Hm, just fixing missing void in fun prototype and only macOS build reported -Werror,-Wstrict-prototypes. I didn't check the workflow files yet. Is this expected?

2025-02-28T22:31:14.8856250Z parser_md.c:23:21: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
2025-02-28T22:31:14.8932860Z    23 | static void usage_md();
2025-02-28T22:31:14.8964640Z       |                     ^
2025-02-28T22:31:14.8964990Z       |                      void
2025-02-28T22:31:14.8965540Z parser_md.c:35:14: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
2025-02-28T22:31:14.8966040Z    35 | void usage_md()
2025-02-28T22:31:14.8966290Z       |              ^
2025-02-28T22:31:14.8966520Z       |               void
2025-02-28T22:31:14.8966750Z 2 errors generated.
2025-02-28T22:31:14.8967050Z make[3]: *** [OBJ.aarch64-apple-darwin20.0.0/parser_md.o] Error 1

[echoix]

It's the only one running clang, and they find different things. We had Travis, but it was an older clang version anyways.

[petrasovaa]

Why are the names inconsistent now?

[wenzeslaus]

The API is the same in both cases G__usage_rest and G__usage_markdown. The only difference is that G__usage_markdown calls static usage_md while G__usage_rest provides the implementation directly. I just kept code structure which is also common elsewhere, but it is not needed here now. I can clean that up so that there is no jump from the API function to static function and there is only one function. That will raise less questions.