CURL_SIZEOF_CURL_SOCKLEN_T can be removed indeed. I think it can be done as a follow-up by a person who use autotools to build CURL and have some experience with the language, because some related code should be removed too.
I'm not so sure about CURL_TYPEOF_CURL_SOCKLEN_T. CURL_TYPEOF_CURL_SOCKLEN_T defined at compile time for almost all cases except few, so probably the value of CURL_TYPEOF_CURL_SOCKLEN_T defined by autotools sometimes used (?):
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.