Make psql_crosstab plans more stable

To achieve this, ANALYZE the data table before querying it, as suggested
by Tom Lane.  On my system, this enables the test to pass with 128 kB of
work_mem (a value with which other tests fail -- so it seems good
enough).

Reported by Michaël Paquier.

src/test/regress/expected/psql_crosstab.out

@@ -10,6 +10,8 @@ VALUES
    ('v0','h4','dbl', -3, '2014-12-15'),
    ('v0',NULL,'qux', 5, '2014-07-15'),
    ('v1','h2','quux',7, '2015-04-04');
+-- make plans more stable
+ANALYZE ctv_data;
 -- running \crosstabview after query uses query in buffer
 SELECT v, EXTRACT(year FROM d), count(*)
  FROM ctv_data

src/test/regress/sql/psql_crosstab.sql

@@ -12,6 +12,9 @@ VALUES
    ('v0',NULL,'qux', 5, '2014-07-15'),
    ('v1','h2','quux',7, '2015-04-04');
 
+-- make plans more stable
+ANALYZE ctv_data;
+
 -- running \crosstabview after query uses query in buffer
 SELECT v, EXTRACT(year FROM d), count(*)
  FROM ctv_data