Fix up the function/variable names in page-ext.el

* lisp/textmodes/page-ext.el (previous-page)
(search-pages)
(sort-pages-in-region)
(sort-pages-buffer)
(pages-sort-buffer)
(pages-set-delimiter): Rename to have pages- prefixes and make the
previous name into aliases for the new names.
(ctl-x-ctl-p-map): Use the new command names.
1 job for master in 90 minutes and 1 second (queued for 2 seconds)
Status Job ID Name Coverage
  Test
failed #2279
test-all

01:30:01

 
Name Stage Failure
failed
test-all Test The script exceeded the maximum execution time set for the job
  GEN      lisp/mail/uudecode-tests.log
ELC lisp/makesum-tests.elc
GEN lisp/makesum-tests.log
ELC lisp/man-tests.elc
GEN lisp/man-tests.log
ELC lisp/md4-tests.elc
GEN lisp/md4-tests.log
Pulling docker image gitlab/gitlab-runner-helper:x86_64-f100a208 ...
ERROR: Job failed: execution took longer than 1h30m0s seconds