qemu/queue.h: leave head structs anonymous unless necessary

Most list head structs need not be given a name.  In most cases the
name is given just in case one is going to use QTAILQ_LAST, QTAILQ_PREV
or reverse iteration, but this does not apply to lists of other kinds,
and even for QTAILQ in practice this is only rarely needed.  In addition,
we will soon reimplement those macros completely so that they do not
need a name for the head struct.  So clean up everything, not giving a
name except in the rare case where it is necessary.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/vl.c b/vl.c
index a903619..9b8ea3f 100644
--- a/vl.c
+++ b/vl.c
@@ -1529,7 +1529,7 @@
     QLIST_ENTRY (vm_change_state_entry) entries;
 };
 
-static QLIST_HEAD(vm_change_state_head, vm_change_state_entry) vm_change_state_head;
+static QLIST_HEAD(, vm_change_state_entry) vm_change_state_head;
 
 VMChangeStateEntry *qemu_add_vm_change_state_handler(VMChangeStateHandler *cb,
                                                      void *opaque)