get/setReadOnly broken if default_transaction_read_only on

Hi,

I've found this in the git head so it applies to current versions.

AbstractJdbc2Connection initializes its readOnly member to a
hardcoded false instead of to 'show default_transaction_read_only'
from the backend.

That means two things: 1. getReadOnly() is wrong in case the
backend has default_transaction_read_only on, and

2. setReadOnly(false) doesn't work in that case, because the value
is compared to readOnly and looks the same, so no set session
characteristics command is sent to the backend.

An application can work around (2) by always calling
setReadOnly(true);setReadOnly(false); if it wants to write.
But that's a bit ugly.

The driver could do that too for a quick hack, but it would
be nice to query the correct value from the backend and use that.

Cheers,
Chapman Flack