qapi: Split machine.json off misc.json

Move commands cpu-add, query-cpus, query-cpus-fast,
query-current-machine, query-hotpluggable-cpus, query-machines,
query-memdev, and set-numa-node with their types from misc.json to new
machine.json.  Also move types X86CPURegister32 and
X86CPUFeatureWordInfo.  Add machine.json to MAINTAINERS section
"Machine core".

Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190619201050.19040-9-armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

qapi/qapi-schema.json

@@ -99,6 +99,7 @@
 { 'include': 'introspect.json' }
 { 'include': 'qom.json' }
 { 'include': 'qdev.json' }
+{ 'include': 'machine.json' }
 { 'include': 'misc.json' }
 { 'include': 'target.json' }
 { 'include': 'audio.json' }