misc/release-checklist: Import from xenbits:~xen/release-checklist

misc/release-checklist: Import from xenbits:~xen/release-checklist

This checklist is what we use when releasing, branching, and making
tarballs.  Right I want to commit an exact copy of the live copy kept
on xenbits outside version control.  I am fed up of maintaining this
outside version control, and probably xen.git is the best place to put
it.

I have reviewed the contents and while it contains much that might be
considered embarrassing, it doesn't contain any secrets :-).

I suggest that:

 * This file should live in misc/ rather than docs/ on the grounds
   that no-one else is likely to ever want it.

 * We maintain the copy in xen.git#staging as the master copy for all
   branches.  When things change they are more often changes to
   infrastructure organisation and so on.  So the file will continue
   to contain explicit treatment for old Xen branches.

 * We will not retain information about branches which are out of
   security support.  (So some of what is there can be deleted at our
   leisure.)

 * This file will be maintained by the release technicians (currently
   mostly that means me, although others have done some parts of the
   task) and commits will be made by release technicians without
   further review or acks.

Please argue about the filename :-).

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Andrew Cooper <andrew.cooper3@citrix.com>
CC: George Dunlap <George.Dunlap@eu.citrix.com>
CC: Jan Beulich <jbeulich@suse.com>
CC: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Tim Deegan <tim@xen.org>
CC: Wei Liu <wei.liu2@citrix.com>