Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2021-09-03' into staging

QAPI patches patches for 2021-09-03

# gpg: Signature made Fri 03 Sep 2021 16:20:49 BST
# 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]
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867  4E5F 3870 B400 EB91 8653

* remotes/armbru/tags/pull-qapi-2021-09-03:
  qapi: Tweak error messages for unknown / conflicting 'if' keys
  qapi: Tweak error messages for missing / conflicting meta-type
  tests/qapi-schema: Hide OrderedDict in test output
  qapi: Use re.fullmatch() where appropriate
  qapi: Use "not COND" instead of "!COND" for generated documentation
  qapi: Avoid redundant parens in code generated for conditionals
  qapi: Factor common recursion out of cgen_ifcond(), docgen_ifcond()
  qapi: Fix C code generation for 'if'
  tests/qapi-schema: Demonstrate broken C code for 'if'
  tests/qapi-schema: Correct two 'if' conditionals
  qapi: Simplify how QAPISchemaIfCond represents "no condition"
  qapi: Simplify QAPISchemaIfCond's interface for generating C
  qapi: Set boolean value correctly in examples

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