qobject: Replace qobject_incref/QINCREF qobject_decref/QDECREF

Now that we can safely call QOBJECT() on QObject * as well as its
subtypes, we can have macros qobject_ref() / qobject_unref() that work
everywhere instead of having to use QINCREF() / QDECREF() for QObject
and qobject_incref() / qobject_decref() for its subtypes.

The replacement is mechanical, except I broke a long line, and added a
cast in monitor_qmp_cleanup_req_queue_locked().  Unlike
qobject_decref(), qobject_unref() doesn't accept void *.

Note that the new macros evaluate their argument exactly once, thus no
need to shout them.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180419150145.24795-4-marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Rebased, semantic conflict resolved, commit message improved]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 3cf2a16..c634dca 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -198,21 +198,21 @@
     } else {
         pm->s3_disabled = false;
     }
-    qobject_decref(o);
+    qobject_unref(o);
     o = object_property_get_qobject(obj, ACPI_PM_PROP_S4_DISABLED, NULL);
     if (o) {
         pm->s4_disabled = qnum_get_uint(qobject_to(QNum, o));
     } else {
         pm->s4_disabled = false;
     }
-    qobject_decref(o);
+    qobject_unref(o);
     o = object_property_get_qobject(obj, ACPI_PM_PROP_S4_VAL, NULL);
     if (o) {
         pm->s4_val = qnum_get_uint(qobject_to(QNum, o));
     } else {
         pm->s4_val = false;
     }
-    qobject_decref(o);
+    qobject_unref(o);
 
     pm->pcihp_bridge_en =
         object_property_get_bool(obj, "acpi-pci-hotplug-with-bridge-support",
@@ -570,7 +570,7 @@
         }
     }
     aml_append(parent_scope, method);
-    qobject_decref(bsel);
+    qobject_unref(bsel);
 }
 
 /**
@@ -2614,12 +2614,12 @@
         return false;
     }
     mcfg->mcfg_base = qnum_get_uint(qobject_to(QNum, o));
-    qobject_decref(o);
+    qobject_unref(o);
 
     o = object_property_get_qobject(pci_host, PCIE_HOST_MCFG_SIZE, NULL);
     assert(o);
     mcfg->mcfg_size = qnum_get_uint(qobject_to(QNum, o));
-    qobject_decref(o);
+    qobject_unref(o);
     return true;
 }