pgsql: only set bytea_output on connect if required
pgsql: only set bytea_output on connect if required

PostgreSQL 9.0 changed the default output for bytea from 'escape' to
'hex', and PHP does not handle data properly if compiled with postgres
library < 9.2.

Reference
- https://bugs.php.net/bug.php?id=59831
- https://bugs.horde.org/ticket/10919#c4

So setting bytea_output=escape is only needed when server >= 9.0 and
client < 9.2.

ipso/ADOdb,ipso/ADOdb