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>
diff --git a/migration/Makefile.objs b/migration/Makefile.objs
index 90f8c1f..1c7770d 100644
--- a/migration/Makefile.objs
+++ b/migration/Makefile.objs
@@ -2,7 +2,7 @@
 common-obj-y += tls.o channel.o savevm.o
 common-obj-y += colo-comm.o colo.o colo-failover.o
 common-obj-y += vmstate.o vmstate-types.o page_cache.o
-common-obj-y += qemu-file.o
+common-obj-y += qemu-file.o global_state.o
 common-obj-y += qemu-file-channel.o
 common-obj-y += xbzrle.o postcopy-ram.o
 common-obj-y += qjson.o