Revert "qapi-events: add 'if' condition to implicit event enum"

Revert "qapi-events: add 'if' condition to implicit event enum"

This reverts commit 7bd263490590ee6fcf34ecb6203437e22f6e5a9c.

The commit applied the events' conditions to the members of enum
QAPIEvent.  Awkward, because it renders QAPIEvent unusable in
target-independent code as soon as we make an event target-dependent.
Reverting this has the following effects:

* ui/vnc.c can remain target independent.

* monitor_qapi_event_conf[] doesn't have to muck around with #ifdef.

* query-events again doesn't reflect conditionals.  I'm going to
  deprecate it in favor of query-qmp-schema.

Another option would be to split target-dependent parts off enum
QAPIEvent into a target-dependent enum.  Doesn't seem worthwhile right
now.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20190214152251.2073-17-armbru@redhat.com>