migration: create global_state.c

It don't belong anywhere else, just the global state where everybody
can stick other things.

Signed-off-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
10 files changed