Merge branch 'dt/smart-http-detect-server-going-away' into maint

When the http server gives an incomplete response to a smart-http rpc call, it could lead to client waiting for a full response that will never come. Teach the client side to notice this condition and abort the transfer. An improvement counterproposal has failed. cf. <20161114194049.mktpsvgdhex2f4zv@sigill.intra.peff.net> * dt/smart-http-detect-server-going-away: upload-pack: optionally allow fetching any sha1 remote-curl: don't hang when a server dies before any output