Improve compatibility when receiving drops from early XDND programs

* lisp/x-dnd.el (x-dnd-handle-xdnd): Save version in state.
If version is less than 5, don't put action and success in
XdndFinished events.  If less than 2, always use `copy' as
the selected action.
10 jobs for master in 207 minutes and 40 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Build Images
passed #47625
build-image-inotify

01:28:18

 
  Normal
passed #47626
test-all-inotify

00:59:34

 
  Platform Images
passed #47627
build-image-filenotify-gio

01:33:31

failed #47628
build-image-gnustep

00:02:14

 
  Platforms
passed #47629
test-filenotify-gio

00:15:18

skipped #47630
test-gnustep
 
  Native Comp Images
passed #47631
build-native-comp-speed0

02:10:20

failed #47632
build-native-comp-speed1

00:02:16

passed #47633
build-native-comp-speed2

02:42:46

 
  Native Comp
passed #47634
test-native-comp-speed0

01:17:14

 
Name Stage Failure
failed
build-native-comp-speed1 Native Comp Images
 > [internal] load build context:
------
rpc error: code = Canceled desc = grpc: the client connection is closing
Running after script...
$ test -n "$(docker ps -aq -f name=${test_name})" && docker cp ${test_name}:checkout/test ${test_name}
$ test -n "$(docker ps -aq -f name=${test_name})" && docker rm ${test_name}
find: build-native-comp-speed1-4ce23228: No such file or directory
$ find ${test_name} ! \( -name "*.log" -o -name ${EMACS_TEST_JUNIT_REPORT} \) -type f -delete
ERROR: Job failed: exit code 1
failed
build-image-gnustep Platform Images
 > [internal] load build context:
------
rpc error: code = Canceled desc = grpc: the client connection is closing
Running after script...
$ test -n "$(docker ps -aq -f name=${test_name})" && docker cp ${test_name}:checkout/test ${test_name}
$ test -n "$(docker ps -aq -f name=${test_name})" && docker rm ${test_name}
$ find ${test_name} ! \( -name "*.log" -o -name ${EMACS_TEST_JUNIT_REPORT} \) -type f -delete
find: build-image-gnustep-4ce23228: No such file or directory
ERROR: Job failed: exit code 1