Set serial when filtering XI_KeyPress events

This fixes fcitx flicker for whatever reason.

* src/xterm.c (handle_one_xevent): Set serial when filtering
XI_KeyPress events.
10 jobs for master in 481 minutes and 43 seconds (queued for 13 seconds)
Status Job ID Name Coverage
  Build Images
passed #33880
build-image-inotify

01:57:26

 
  Normal
failed #33881
test-all-inotify

04:00:06

 
  Platform Images
passed #33882
build-image-filenotify-gio

02:00:10

failed #33883
build-image-gnustep

00:29:10

 
  Platforms
failed #33884
test-filenotify-gio

00:15:19

skipped #33885
test-gnustep
 
  Native Comp Images
passed #33886
build-native-comp-speed0

05:59:37

passed #33887
build-native-comp-speed1

02:39:33

passed #33888
build-native-comp-speed2

03:09:09

 
  Native Comp
failed #33889
test-native-comp-speed0

00:53:37

 
Name Stage Failure
failed
test-native-comp-speed0 Native Comp
Makefile:313: recipe for target 'check' failed
make: Leaving directory '/checkout/test'
make[1]: *** [check-doit] Error 1
make: *** [check] Error 2
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}
test-native-comp-speed0-b469a015
ERROR: Job failed: exit code 2
failed
test-all-inotify Normal The script exceeded the maximum execution time set for the job
  GEN      src/marker-tests.log
ELC src/minibuf-tests.elc
GEN src/minibuf-tests.log
ELC src/print-tests.elc
GEN src/print-tests.log
ELC src/process-tests.elc
GEN src/process-tests.log
Pulling docker image gitlab/gitlab-runner-helper:x86_64-d0b76032 ...
ERROR: Job failed: execution took longer than 4h0m0s seconds
failed
test-filenotify-gio Platforms
  SKIPPED  file-notify-test10-sufficient-resources  ((skip-unless (string-equal (file-notify--test-library) "kqueue")) :form (string-equal "gfilenotify" "kqueue") :value nil :explanation (arrays-of-different-length 11 6 "gfilenotify" "kqueue" first-mismatch-at 0))
SKIPPED file-notify-test10-sufficient-resources-remote ((skip-unless (string-equal (file-notify--test-library) "kqueue")) :form (string-equal "gio" "kqueue") :value nil :explanation (arrays-of-different-length 3 6 "gio" "kqueue" first-mismatch-at 0))

make: Leaving directory '/checkout/test'
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}
test-filenotify-gio-b469a015
ERROR: Job failed: exit code 2
failed
build-image-gnustep Platform Images
#12 ERROR: executor failed running [/bin/sh -c make bootstrap]: exit code: 2
------
> [emacs-gnustep 5/5] RUN make bootstrap:
------
executor failed running [/bin/sh -c make bootstrap]: exit code: 2
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}
ERROR: Job failed: exit code 1