Support for JSON mode monitor

Initial support for the new QEMU monitor protocol  using JSON
as the data encoding format instead of plain text

* po/POTFILES.in: Add src/qemu/qemu_monitor_json.c
* src/qemu/qemu_conf.c, src/qemu/qemu_conf.h: Hack to turn on QMP
  mode. Replace with a version number check on >= 0.12 later
* src/qemu/qemu_monitor.c: Delegate to json monitor if enabled
* src/qemu/qemu_monitor_json.c, src/qemu/qemu_monitor_json.h: Add
  impl of QMP protocol
* src/Makefile.am: Add src/qemu/qemu_monitor_json.{c,h}

tests/qemuxml2argvtest.c

@@ -60,7 +60,7 @@ static int testCompareXMLToArgvFiles(const char *xml,
         goto fail;
 
     if (qemudBuildCommandLine(NULL, &driver,
-                              vmdef, &monitor_chr, flags,
+                              vmdef, &monitor_chr, 0, flags,
                               &argv, &qenv,
                               NULL, NULL, migrateFrom) < 0)
         goto fail;