CURRENT_TIMESTAMP still quoted in default

[robintheander]

SQL/Translator/Producer/PostgreSQL.pm has this line:

'CURRENT_TIMESTAMP' => 'CURRENT_TIMESTAMP',

It causes the string to be quoted regardless of a ref or string is passed to default_value. A reference must be generated by the _apply_default_value function, so the line should be changed to:

'CURRENT_TIMESTAMP' => \'CURRENT_TIMESTAMP',

In fact, the 'now()' replacement should also be a ref and the replacement should add the other Pg datetime variants: CURRENT_TIME, CURRENT_DATE, LOCALTIME, LOCALSTAMP. There might even be other Pg magic functions that should be added.