obfs4 breaks http proxy with basic auth

When connecting through an http proxy with basic auth, the client (tor) should send an HTTP request with header "Proxy-Authorization: Basic " (rfc 7235), but instead tor uses something defined for basic auth with http servers, like "Authorization: Basic ". For a proxy like squid (at least) this means it cannot connect to the relay network as it keeps receiving error 407 (auth required)

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Username: gilcu3