tools/libxl: rename remus device to checkpoint device

tools/libxl: rename remus device to checkpoint device

This patch is auto generated by the following commands:
 1. git mv tools/libxl/libxl_remus_device.c tools/libxl/libxl_checkpoint_device.c
 2. perl -pi -e 's/libxl_remus_device/libxl_checkpoint_device/g' tools/libxl/Makefile
 3. perl -pi -e 's/\blibxl__remus_devices/libxl__checkpoint_devices/g' tools/libxl/*.[ch]
 4. perl -pi -e 's/\blibxl__remus_device\b/libxl__checkpoint_device/g' tools/libxl/*.[ch]
 5. perl -pi -e 's/\blibxl__remus_device_instance_ops\b/libxl__checkpoint_device_instance_ops/g' tools/libxl/*.[ch]
 6. perl -pi -e 's/\blibxl__remus_callback\b/libxl__checkpoint_callback/g' tools/libxl/*.[ch]
 7. perl -pi -e 's/\bremus_device_init\b/checkpoint_device_init/g' tools/libxl/*.[ch]
 8. perl -pi -e 's/\bremus_devices_setup\b/checkpoint_devices_setup/g' tools/libxl/*.[ch]
 9. perl -pi -e 's/\bdefine_remus_checkpoint_api\b/define_checkpoint_api/g' tools/libxl/*.[ch]
10. perl -pi -e 's/\brds\b/cds/g' tools/libxl/*.[ch]
11. perl -pi -e 's/REMUS_DEVICE/CHECKPOINT_DEVICE/g' tools/libxl/*.[ch] tools/libxl/*.idl
12. perl -pi -e 's/REMUS_DEVOPS/CHECKPOINT_DEVOPS/g' tools/libxl/*.[ch] tools/libxl/*.idl
13. perl -pi -e 's/\bremus\b/checkpoint/g' tools/libxl/libxl_checkpoint_device.[ch]
14. perl -pi -e 's/\bremus device/checkpoint device/g' tools/libxl/libxl_internal.h
15. perl -pi -e 's/\bRemus device/checkpoint device/g' tools/libxl/libxl_internal.h
16. perl -pi -e 's/\bremus abstract/checkpoint abstract/g' tools/libxl/libxl_internal.h
17. perl -pi -e 's/\bremus invocation/checkpoint invocation/g' tools/libxl/libxl_internal.h
18. perl -pi -e 's/\blibxl__remus_device_\(/libxl__checkpoint_device_(/g' tools/libxl/libxl_internal.h

The patch also fixes the following backword compatibility:
  The error code ERROR_REMUS_XXX was introduced in Xen 4.5, and
  changed to ERROR_CHECKPOINT_XXX after previous renaming.

Signed-off-by: Wen Congyang <wency@cn.fujitsu.com>
Signed-off-by: Yang Hongyang <hongyang.yang@easystack.cn>
Reviewed-Lightly-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>