Eliminates a future compilation error when UI code includes the tracing
headers (indirectly pulling "disas/bfd.h" through "qom/cpu.h") and
GLib's i18n '_' macro.

Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>