[winswitch] python2-xxhash package for CentOS

[Frank, Bradley]

When patching today, I noticed that python2-pynvml and python2-xxhash were
now a dependency (python2-xxhash as per
https://www.xpra.org/trac/changeset/13980/xpra). I see you offer pynvml as
part of your CentOS repo, but not xxhash (only in Fedora 25 did I find it).
Is there any plans to include this package for CentOS? We're currently
running 6.8 and having the dependency available through the xpra repo is
incredibly beneficial.

Thank you,

-- 
Brad Frank
Systems Administrator