HTTPS proxies - support for own SSL/TLS session
HTTPS proxies - support for own SSL/TLS session

Add support for own SSL/TLS settings for HTTPS proxy,
which might be separate from general SSL/TLS settings.
Supported since libcurl 7.52.0.

Original commit link:
https://github.com/curl/curl/commit/cb4e2be7c6d42ca0780f8e0a747cecf9ba45f151

typhoeus/ethon