Re: psql tab-completion for new syntax

Here is a patch to support new syntax in psql tab completion
and fix bugs to complete after an open parenthesis.

Supported additonal syntax are:
- ALTER TABLE/INDEX/TABLESPACE SET/RESET with options
- ALTER TABLE ALTER COLUMN SET/RESET with options
- ALTER TABLE ALTER COLUMN SET STORAGE
- CREATE TRIGGER with events
- CREATE INDEX CONCURRENTLY
- CREATE INDEX ON (without name)
- CREATE INDEX ... USING with pg_am.amname instead of hard-corded names.

Fixes bugs are:
Bug 1: Double parenthesis
=# INSERT INTO pgbench_history VALUES (<TAB>
=# INSERT INTO pgbench_history VALUES (( <= wrong

Bug 2: We cannot complete words if no whitespaces around a parenthesis.
=# CREATE INDEX idx ON pgbench_history( <TAB>
^ no whitespace here

Bug 3: should be completed with "(" before columns.
=# CREATE INDEX foo ON pgbench_accounts USING BTREE <TAB>
abalance aid bid filler <= wrong, should be "("

I adjusted previous_word() to split words not only with spaces but also
with non-alphabets, and removed a hack with find_open_parenthesis().

Comments?

Regards,
---
Takahiro Itagaki
NTT Open Source Software Center