TODO: remove IDNA2008

 1.7 Detect when called from within callbacks

 1.8 Allow SSL (HTTPS) to proxy

 1.9 Cache negative name resolves

 1.10 Support IDNA2008

 1.11 minimize dependencies with dynamicly 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 Support IDNA2008

 International Domain Names are supported in libcurl since years back, powered

 by libidn. libidn implements IDNA2003 which has been superseded by IDNA2008.

 libidn2 is an existing library offering support for IDNA2008.

1.11 minimize dependencies with dynamicly loaded modules

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