erlang: allow remote attackers to redirect an application's outbound HTTP traffic to an arbitrary proxy serve

inets in Erlang possibly 22.1 and earlier follows RFC 3875 section 4.1.18 and therefore does not protect applications from the presence of untrusted client data in the HTTP_PROXY environment variable, which might allow remote attackers to redirect an application's outbound HTTP traffic to an arbitrary proxy server via a crafted Proxy header in an HTTP request, aka an "httpoxy" issue.