TODO: 1.10 auto-detect proxy

 1.7 Detect when called from within callbacks

 1.8 CURLOPT_RESOLVE for any port number

 1.9 Cache negative name resolves

 1.10 auto-detect proxy

 1.11 minimize dependencies with dynamically loaded modules

 1.12 have form functions use CURL handle argument

 1.14 Typesafe curl_easy_setopt()

 A name resolve that has failed is likely to fail when made again within a

 short period of time. Currently we only cache positive responses.

1.10 auto-detect proxy

 libcurl could be made to detect the system proxy setup automatically and use

 that. On Windows, macOS and Linux desktops for example.

 The pull-request to use libproxy for this was deferred due to doubts on the

 reliability of the dependency and how to use it:

 https://github.com/curl/curl/pull/977

 libdetectproxy is a (C++) library for detecting the proxy on Windows

 https://github.com/paulharris/libdetectproxy

1.11 minimize dependencies with dynamically loaded modules

 We can create a system with loadable modules/plug-ins, where these modules