Tighten up a couple of regression test cases that can have platform-dependent

results due to underspecified ordering.  Per report from buildfarm member
pika.

src/test/regress/expected/window.out

@@ -233,26 +233,27 @@ SELECT cume_dist() OVER (PARTITION BY four ORDER BY ten), ten, four FROM tenk1 W
                  1 |   3 |    3
 (10 rows)
 
-SELECT ntile(3) OVER (ORDER BY ten), ten, four FROM tenk1 WHERE unique2 < 10;
+SELECT ntile(3) OVER (ORDER BY ten, four), ten, four FROM tenk1 WHERE unique2 < 10;
  ntile | ten | four 
 -------+-----+------
      1 |   0 |    0
-     1 |   0 |    2
      1 |   0 |    0
+     1 |   0 |    2
      1 |   1 |    1
-     2 |   1 |    3
      2 |   1 |    1
+     2 |   1 |    3
      2 |   3 |    3
      3 |   4 |    0
      3 |   7 |    1
      3 |   9 |    1
 (10 rows)
 
-SELECT ntile(NULL) OVER (ORDER BY ten), ten, four FROM tenk1 LIMIT 1;
+SELECT ntile(NULL) OVER (ORDER BY ten, four), ten, four FROM tenk1 LIMIT 2;
  ntile | ten | four 
 -------+-----+------
        |   0 |    0
-(1 row)
+       |   0 |    0
+(2 rows)
 
 SELECT lag(ten) OVER (PARTITION BY four ORDER BY ten), ten, four FROM tenk1 WHERE unique2 < 10;
  lag | ten | four 

src/test/regress/sql/window.sql

@@ -54,9 +54,9 @@ SELECT percent_rank() OVER (PARTITION BY four ORDER BY ten), ten, four FROM tenk
 
 SELECT cume_dist() OVER (PARTITION BY four ORDER BY ten), ten, four FROM tenk1 WHERE unique2 < 10;
 
-SELECT ntile(3) OVER (ORDER BY ten), ten, four FROM tenk1 WHERE unique2 < 10;
+SELECT ntile(3) OVER (ORDER BY ten, four), ten, four FROM tenk1 WHERE unique2 < 10;
 
-SELECT ntile(NULL) OVER (ORDER BY ten), ten, four FROM tenk1 LIMIT 1;
+SELECT ntile(NULL) OVER (ORDER BY ten, four), ten, four FROM tenk1 LIMIT 2;
 
 SELECT lag(ten) OVER (PARTITION BY four ORDER BY ten), ten, four FROM tenk1 WHERE unique2 < 10;