Make REs in magic-(fallback-)mode-alist case-sensitive.

These variables are used for well-defined file formats where relaxed
case matching is not wanted usually.

* lisp/files.el (magic-mode-alist, magic-fallback-mode-alist): Update
the doc string.
(set-auto-mode): Make looking-at for elements of magic-mode-alist and
magic-fallback-mode-alist use case-fold-search == nil.
* lisp/files.el (files-test-magic-mode-alist-re-baseline)
(files-test-magic-mode-alist-re-no-match)
(files-test-magic-mode-alist-re-case-diff): Add.
1 job for master in 90 minutes and 1 second (queued for 3 seconds)
Status Job ID Name Coverage
  Test
failed #2626
test-all

01:30:01

 
Name Stage Failure
failed
test-all Test The script exceeded the maximum execution time set for the job
make -C test check-expensive
make[1]: Entering directory '/builds/emacs/emacs/test'
rm -f ./*.tmp
make[2]: Entering directory '/builds/emacs/emacs/test'
make[3]: Entering directory '/builds/emacs/emacs/test'
ELC lisp/net/tramp-tests.elc
GEN lisp/net/tramp-tests.log
Pulling docker image gitlab/gitlab-runner-helper:x86_64-d0b76032 ...
ERROR: Job failed: execution took longer than 1h30m0s seconds