tests: use "compare exp out", not "compare out exp"

tests: use "compare exp out", not "compare out exp"

Likewise, when an empty file is expected, use "compare /dev/null out",
not "compare out /dev/null". I.e., specify the expected/desired contents
via the first file name.  Prompted by a suggestion from Bruno Haible
in http://thread.gmane.org/gmane.comp.gnu.grep.bugs/4020/focus=29154

Run these commands:

    git grep -l -E 'compare [^ ]+ exp' \
      |xargs perl -pi -e 's/(compare) (\S+) (exp\S*)/$1 $3 $2/'
    git grep -l -E 'compare [^ ]+ /dev/null' \
      |xargs perl -pi -e 's/(compare) (\S+) (\/dev\/null)/$1 $3 $2/'

* tests/chgrp/no-x: As above.
* tests/chmod/no-x: Likewise.
* tests/chmod/silent: Likewise.
* tests/chmod/thru-dangling: Likewise.
* tests/chown/basic: Likewise.
* tests/chown/deref: Likewise.
* tests/chown/preserve-root: Likewise.
* tests/cp/abuse: Likewise.
* tests/cp/backup-is-src: Likewise.
* tests/cp/cp-a-selinux: Likewise.
* tests/cp/cp-mv-enotsup-xattr: Likewise.
* tests/cp/fail-perm: Likewise.
* tests/cp/into-self: Likewise.
* tests/cp/proc-zero-len: Likewise.
* tests/cp/src-base-dot: Likewise.
* tests/cp/thru-dangling: Likewise.
* tests/dd/reblock: Likewise.
* tests/dd/unblock-sync: Likewise.
* tests/du/2g: Likewise.
* tests/du/8gb: Likewise.
* tests/du/basic: Likewise.
* tests/du/bigtime: Likewise.
* tests/du/deref-args: Likewise.
* tests/du/exclude: Likewise.
* tests/du/files0-from-dir: Likewise.
* tests/du/hard-link: Likewise.
* tests/du/inacc-dest: Likewise.
* tests/du/inacc-dir: Likewise.
* tests/du/long-sloop: Likewise.
* tests/du/max-depth: Likewise.
* tests/du/move-dir-while-traversing: Likewise.
* tests/du/no-deref: Likewise.
* tests/du/no-x: Likewise.
* tests/du/one-file-system: Likewise.
* tests/du/slash: Likewise.
* tests/du/trailing-slash: Likewise.
* tests/install/strip-program: Likewise.
* tests/ln/hard-backup: Likewise.
* tests/ls/block-size: Likewise.
* tests/ls/color-clear-to-eol: Likewise.
* tests/ls/color-dtype-dir: Likewise.
* tests/ls/color-norm: Likewise.
* tests/ls/dangle: Likewise.
* tests/ls/dired: Likewise.
* tests/ls/file-type: Likewise.
* tests/ls/follow-slink: Likewise.
* tests/ls/infloop: Likewise.
* tests/ls/m-option: Likewise.
* tests/ls/no-arg: Likewise.
* tests/ls/recursive: Likewise.
* tests/ls/rt-1: Likewise.
* tests/ls/stat-dtype: Likewise.
* tests/ls/stat-failed: Likewise.
* tests/ls/stat-free-symlinks: Likewise.
* tests/ls/x-option: Likewise.
* tests/misc/arch: Likewise.
* tests/misc/cat-buf: Likewise.
* tests/misc/cat-proc: Likewise.
* tests/misc/chcon: Likewise.
* tests/misc/csplit: Likewise.
* tests/misc/df-P: Likewise.
* tests/misc/fmt-long-line: Likewise.
* tests/misc/groups-dash: Likewise.
* tests/misc/groups-version: Likewise.
* tests/misc/head-pos: Likewise.
* tests/misc/nl: Likewise.
* tests/misc/od-N: Likewise.
* tests/misc/od-multiple-t: Likewise.
* tests/misc/od-x8: Likewise.
* tests/misc/printf: Likewise.
* tests/misc/printf-hex: Likewise.
* tests/misc/pwd-option: Likewise.
* tests/misc/readlink-fp-loop: Likewise.
* tests/misc/runcon-no-reorder: Likewise.
* tests/misc/seq-long-double: Likewise.
* tests/misc/sort-NaN-infloop: Likewise.
* tests/misc/sort-benchmark-random: Likewise.
* tests/misc/sort-debug-keys: Likewise.
* tests/misc/sort-float: Likewise.
* tests/misc/sort-merge-fdlimit: Likewise.
* tests/misc/sort-unique-segv: Likewise.
* tests/misc/stat-hyphen: Likewise.
* tests/misc/stat-slash: Likewise.
* tests/misc/stdbuf: Likewise.
* tests/misc/sum-sysv: Likewise.
* tests/misc/tac-2-nonseekable: Likewise.
* tests/misc/tac-continue: Likewise.
* tests/misc/tr-case-class: Likewise.
* tests/misc/truncate-fail-diag: Likewise.
* tests/misc/wc-files0: Likewise.
* tests/mkdir/selinux: Likewise.
* tests/mv/backup-dir: Likewise.
* tests/mv/backup-is-src: Likewise.
* tests/mv/diag: Likewise.
* tests/mv/dir2dir: Likewise.
* tests/mv/dup-source: Likewise.
* tests/mv/force: Likewise.
* tests/mv/hard-verbose: Likewise.
* tests/mv/i-link-no: Likewise.
* tests/mv/into-self: Likewise.
* tests/mv/into-self-2: Likewise.
* tests/mv/into-self-3: Likewise.
* tests/mv/mv-special-1: Likewise.
* tests/mv/part-fail: Likewise.
* tests/mv/perm-1: Likewise.
* tests/mv/sticky-to-xpart: Likewise.
* tests/mv/trailing-slash: Likewise.
* tests/rm/rm1: Likewise.
* tests/rm/rm2: Likewise.
* tests/rm/cycle: Likewise.
* tests/rm/dir-no-w: Likewise.
* tests/rm/dir-nonrecur: Likewise.
* tests/rm/fail-2eperm: Likewise.
* tests/rm/fail-eacces: Likewise.
* tests/rm/i-never: Likewise.
* tests/rm/inaccessible: Likewise.
* tests/rm/interactive-always: Likewise.
* tests/rm/interactive-once: Likewise.
* tests/rm/isatty: Likewise.
* tests/rm/one-file-system: Likewise.
* tests/rm/rm3: Likewise.
* tests/rm/rm5: Likewise.
* tests/rm/unread2: Likewise.
* tests/rm/v-slash: Likewise.
* tests/sample-test: Likewise.
* tests/split/b-chunk: Likewise.
* tests/split/fail: Likewise.
* tests/split/l-chunk: Likewise.
* tests/split/lines: Likewise.
* tests/split/r-chunk: Likewise.
* tests/split/suffix-length: Likewise.
* tests/tail-2/big-4gb: Likewise.
* tests/tail-2/follow-name: Likewise.
* tests/tail-2/follow-stdin: Likewise.
* tests/tail-2/pipe-f: Likewise.
* tests/tail-2/pipe-f2: Likewise.
* tests/tail-2/start-middle: Likewise.
* tests/touch/60-seconds: Likewise.
* tests/touch/fail-diag: Likewise.
* tests/touch/not-owner: Likewise.
* tests/touch/relative: Likewise.