To avoid breaking 3rd-party code reusing these symbols as C++ methods,
e.g. in CMake sources:
```
cmake/src/v4.0.0-b30653ae0c.clean/Source/cmCurl.cxx:119:24: error: expected unqualified-id
119 | ::CURLcode res = ::curl_easy_setopt(curl, CURLOPT_CAINFO, cafile.c_str());
| ^
```
Also expand comment to highlight the case.
Reported-by: Kai Pastor
Bug: daa6b27b4d (r177869049)
Reported-by: Marcel Raad
Bug: https://curl.se/mail/lib-2026-02/0020.htmlFixes#20682
Follow-up to daa6b27b4d#20597Closes#20686