Added support for DESC, NULLS FIRST/LAST, COLLATE to index keys

Previously, pg_reorg could not use the indexes which have DESC,
NULLS FIRST/LAST, COLLATE keywords to index keys.
This was reported as pg_repack issue #3.
With this fix, we have added the handling of these keywords and
regression tests.

In addition, we have changed the generating steps of regression
tests sql files and expected out files because PostgreSQL does
not support COLLATE until 9.0.

The original patch was created by pg_repack developers, and
modified by Amit Langote and Takashi Ohnishi.