pgsql: Make regression test output stable.

Make regression test output stable.

In the test query I added for ALTER TABLE retaining comments, the order of
the result rows was not stable, and varied across systems. Add an ORDER BY
to make the order predictable. This should fix the buildfarm failures.

Branch
------
REL9_5_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/fe92a72a2bf6f485fc9f08c3e6191838ac3c6441

Modified Files
--------------
src/test/regress/expected/alter_table.out |   12 ++++++------
src/test/regress/sql/alter_table.sql      |    8 ++++----
2 files changed, 10 insertions(+), 10 deletions(-)