Modify the way to prepare expected out files for regression tests.

In the regression tests, result out files are compared to expected
out files. Though the output are difference if PG server major
version are different, we need to prepare expected out files for
each PG server versions. Previously we did it in make command
by bin/Makefile. However, we have got to know that we use several expected
out files for one regression test without creating in make commands:
we set the expected out files with suffix like test.out, test_1.out.