Allow rgrep users to indicate case folding easier

* lisp/progmodes/grep.el (rgrep): Allow the user to toggle case
sensitivity interactively (bug#16913).
4 jobs for master in 7 minutes and 39 seconds (queued for 1 minute and 19 seconds)
Status Job ID Name Coverage
  Build Images
failed #47359
build-image-inotify

00:07:39

 
  Normal
skipped #47361
test-lisp-emacs-lisp-inotify
skipped #47360
test-lisp-inotify
skipped #47362
test-lisp-progmodes-inotify
 
Name Stage Failure
failed
build-image-inotify Build Images
$ docker login -u ${CI_REGISTRY_USER} -p ${CI_REGISTRY_PASSWORD} ${CI_REGISTRY}
WARNING! Using --password via the CLI is insecure. Use --password-stdin.
Error response from daemon: Get https://emba.gnu.org:5050/v2/: Get https://emba.gnu.org//jwt/auth?account=gitlab-ci-token&client_id=docker&offline_token=true&service=container_registry: net/http: request canceled (Client.Timeout exceeded while awaiting headers) (Client.Timeout exceeded while awaiting headers)
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-inotify-e418e910: No such file or directory
ERROR: Job failed: exit code 1