configure --enable-debug now enables -Wassign-enum with clang,
identifying several enum "abuses" also fixed.
Reported-by: Gisle Vanem
Bug: 879007f811 (commitcomment-42087553)Closes#5929
const struct curl_easyoption *curl_easy_option_by_name(const char *name);
const struct curl_easyoption *curl_easy_option_by_id (CURLoption id);
const struct curl_easyoption *
curl_easy_option_next(const struct curl_easyoption *prev);
The purpose is to provide detailed enough information to allow for
example libcurl bindings to get option information at run-time about
what easy options that exist and what arguments they expect.
Assisted-by: Jeroen Ooms
Closes#5365
