migration: move skip_configuration out

It was in SaveState but now moved to MigrationState altogether, reverted
its meaning, then renamed to "send_configuration". Again, using
HW_COMPAT_2_3 for old PC/SPAPR machines, and accel_register_prop() for
xen_init().

Removing savevm_skip_configuration().

Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Message-Id: <1498536619-14548-8-git-send-email-peterx@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

include/hw/compat.h

@@ -181,6 +181,10 @@
         .driver   = TYPE_PCI_DEVICE,\
         .property = "x-pcie-lnksta-dllla",\
         .value    = "off",\
+    },{\
+        .driver   = "migration",\
+        .property = "send-configuration",\
+        .value    = "off",\
     },{\
         .driver   = "migration",\
         .property = "store-global-state",\

include/migration/misc.h

@@ -42,7 +42,6 @@ int64_t self_announce_delay(int round)
 
 void dump_vmstate_json_to_file(FILE *out_fp);
 void savevm_skip_section_footers(void);
-void savevm_skip_configuration(void);
 
 /* migration/migration.c */
 void migration_object_init(void);