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

[here, there were none of the latter]

2 files changed, 4 insertions, 4 deletions

diff --git a/testsuite/lid-radix b/testsuite/lid-radix
index 63922ba..918391e 100755
--- a/testsuite/lid-radix
+++ b/testsuite/lid-radix
@@ -40,11 +40,11 @@ for i in d o x; do
 done
 
 lid --key=none 0xff > out || fail=1
-compare out exp.all || fail=1
+compare exp.all out || fail=1
 
 for i in d o x; do
   lid --key=none -$i 0xff > out || fail=1
-  compare out exp.$i || fail=1
+  compare exp.$i out || fail=1
 done
 
 Exit $fail
diff --git a/testsuite/lid-range b/testsuite/lid-range
index 783ba26..10747ec 100755
--- a/testsuite/lid-range
+++ b/testsuite/lid-range
@@ -34,7 +34,7 @@ one            in.txt
 two            in.txt
 EOF
 lid -F ..2 > out || fail=1
-compare out exp || fail=1
+compare exp out || fail=1
 
 cat <<\EOF > exp || framework_failure_
 four           in.txt
@@ -42,6 +42,6 @@ three          in.txt
 two            in.txt
 EOF
 lid -F 2.. > out || fail=1
-compare out exp || fail=1
+compare exp out || fail=1
 
 Exit $fail