Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2018-07-03' into staging

QAPI patches for 2018-07-03

# gpg: Signature made Tue 03 Jul 2018 21:52:55 BST
# gpg:                using RSA key 3870B400EB918653
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>"
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>"
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867  4E5F 3870 B400 EB91 8653

* remotes/armbru/tags/pull-qapi-2018-07-03:
  qapi: add conditions to SPICE type/commands/events on the schema
  qapi: add conditions to VNC type/commands/events on the schema
  qapi: add 'If:' section to generated documentation
  qapi-types: add #if conditions to types & visitors
  qapi/events: add #if conditions to events
  qapi/commands: add #if conditions to commands
  qapi-introspect: add preprocessor conditions to generated QLit
  qapi-introspect: modify to_qlit() to append ',' on level > 0
  qapi: add #if/#endif helpers
  qapi: mcgen() shouldn't indent # lines
  qapi: add 'ifcond' to visitor methods
  qapi: leave the ifcond attribute undefined until check()
  qapi: pass 'if' condition into QAPISchemaEntity objects
  qapi: add 'if' to top-level expressions

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