Include qapi/qmp/qdict.h exactly where needed

This cleanup makes the number of objects depending on qapi/qmp/qdict.h
drop from 4550 (out of 4743) to 368 in my "build everything" tree.
For qapi/qmp/qobject.h, the number drops from 4552 to 390.

While there, separate #include from file comment with a blank line.

Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20180201111846.21846-13-armbru@redhat.com>
diff --git a/tests/tco-test.c b/tests/tco-test.c
index 2616d33..8ab43d7 100644
--- a/tests/tco-test.c
+++ b/tests/tco-test.c
@@ -6,11 +6,13 @@
  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  * See the COPYING file in the top-level directory.
  */
+
 #include "qemu/osdep.h"
 
 #include "libqtest.h"
 #include "libqos/pci.h"
 #include "libqos/pci-pc.h"
+#include "qapi/qmp/qdict.h"
 #include "hw/pci/pci_regs.h"
 #include "hw/i386/ich9.h"
 #include "hw/acpi/ich9.h"