Make :ssh-unknown-hostkey public and support output stream in scp-get#4

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simkoc wants to merge 2 commits intoalxchk:masterfrom

Commits on Jun 17, 2016

made ssh-unknown-hostkey a public exception in packages
Simon Koch
committed

Commits on Oct 27, 2016

added support for streams in the scp-get function
Simon Koch
committed