Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2021-10-29' into staging

QAPI patches patches for 2021-10-29

# gpg: Signature made Fri 29 Oct 2021 12:28:53 PM PDT
# gpg:                using RSA key 354BC8B3D7EB2A6B68674E5F3870B400EB918653
# gpg:                issuer "armbru@redhat.com"
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>" [full]
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>" [full]

* remotes/armbru/tags/pull-qapi-2021-10-29:
  qapi: Extend -compat to set policy for unstable interfaces
  qapi: Factor out compat_policy_input_ok()
  qapi: Generalize enum member policy checking
  qapi: Generalize command policy checking
  qapi: Generalize struct member policy checking
  qapi: Tools for sets of special feature flags in generated code
  qapi: Eliminate QCO_NO_OPTIONS for a slight simplification
  qapi: Mark unstable QMP parts with feature 'unstable'
  qapi: New special feature flag "unstable"

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>