Merge remote-tracking branch 'remotes/qmp-unstable/queue/qmp' into staging

Merge remote-tracking branch 'remotes/qmp-unstable/queue/qmp' into staging

* remotes/qmp-unstable/queue/qmp:
  tests: test-qmp-commands: Fix double free
  qapi script: do not add "_" for every capitalized char in enum
  qapi script: do not allow string discriminator
  qapi: convert BlockdevOptions to use enum discriminator
  qapi script: support enum type as discriminator in union
  qapi script: use same function to generate enum string
  qapi script: code move for generate_enum_name()
  qapi script: check correctness of union
  qapi script: remember line number in schema parsing
  qapi script: add check for duplicated key
  qapi script: remember explicitly defined enum values

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>