Merge branch doc_fixes

  Rebase from
  http://git.kernel.org/pub/scm/linux/kernel/git/mtk/util-linux.git doc_fixes

  docs: renice(1): Add credentials(7) to SEE ALSO
  docs: renice(1): Add SEE ALSO entry for sched(7)
  docs: mount(8): Wording fix
  docs: ionice(1): SEE ALSO: add ioprio_set(2)
  docs: lsns(8): SEE ALSO: add namespaces(7)
  docs: last(1): Eliminate oddball formatting
  docs: last(1): SEE ALSO: add reference to wtmp(5)
  docs: taskset(1): Wording fix
  docs: namei(1): SEE ALSO: add symlink(7)
  docs: kill(1): Wording fix
  docs: various pages: Use 'UID" and "GID", not "uid" and "gid" in man pages
  docs: various pages: Use "PID" not "pid" in man-pages
  docs: various pages: Use "ID" not "id" in man pages
  docs: various pages: Use consistent terminology (set-user-ID and set-group-ID)
  docs: various pages: Format pathnames as italic (.I)