- add `curl_global_init()` and `curl_global_cleanup()` where missing.
- check the result of `curl_global_init()` where missing.
- return the last curl error from `main()`.
- drop Win32-specific socket initialization in favor of `curl_global_init()`.
- rename some outliers to `res` for curl result code.
- fix cleanup in some error cases.
Inspired by Joshua's report on examples.
Closes#19053
Also:
- CURLOPT_HSTS_CTRL.md: sync macro definitions with `curl/curl.h`.
Perhaps it'd be better to delete copies like this?
- keep existing casts within the documentation to make sure it applies
to older curl versions as well.
- CURLOPT_IPRESOLVE.md: re-add a long cast to man page, for consistency
with the above.
Closes#17791
