typedefs: add QJSON

typedefs: add QJSON

Since commit 83ee768d6247b, we now have two places that define the
QJSON type:

$ git grep 'typedef struct QJSON QJSON'
include/migration/vmstate.h:typedef struct QJSON QJSON;
migration/qjson.h:typedef struct QJSON QJSON;

This breaks docker-test-build@centos6:

In file included from /tmp/qemu-test/src/migration/savevm.c:59:
/tmp/qemu-test/src/migration/qjson.h:16: error: redefinition of typedef
 'QJSON'
/tmp/qemu-test/src/include/migration/vmstate.h:30: note: previous
 declaration of 'QJSON' was here
make: *** [migration/savevm.o] Error 1

This happens because CentOS 6 has an old GCC 4.4.7. Even if redefining
a typedef with the same type is permitted since GCC 4.6, unless -pedantic
is passed, we don't really need to do that on purpose. Let's have a
single definition in <qemu/typedefs.h> instead.

Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <152844714981.11789.3657734445739553287.stgit@bahia.lan>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>