Problem with multiple SUMs

After recent changes I find an error with SUM when summing more than
one column.  Here is the test sequence.

DROP TABLE x;
CREATE TABLE x (a int, b int); 
INSERT INTO x VALUES (1, 5);
INSERT INTO x VALUES (2, 7);
SELECT * FROM x;
SELECT SUM(a) FROM x;
SELECT SUM(b) FROM x;
SELECT SUM(a), SUM(b) FROM x;

The last three statements give the following expected results when
run on a system compiled Jan 19.

darcy=> SELECT SUM(a) FROM x;
sum
--- 3
(1 row)

darcy=> SELECT SUM(b) FROM x;
sum
---12
(1 row)

darcy=> SELECT SUM(a), SUM(b) FROM x;
sum|sum
---+--- 3| 12
(1 row)

On a system compiled Jan 27, I see the following.

darcy=> SELECT SUM(a) FROM x;
sum
--- 3
(1 row)

darcy=> SELECT SUM(b) FROM x;
sum
---12
(1 row)

darcy=> SELECT SUM(a), SUM(b) FROM x;
sum|sum
---+---12| 12
(1 row)

See how the individual sums are correct but I can no longer get both
sums in one select.

-- 
D'Arcy J.M. Cain <darcy@{druid|vex}.net>   |  Democracy is three wolves
http://www.druid.net/darcy/                |  and a sheep voting on
+1 416 424 2871     (DoD#0082)    (eNTP)   |  what's for dinner.