Signed-off-by: Roeland Jago Douma <roeland@famdouma.nl>

also simplifies the code and now exactly matches postgresql search rules

When the connection is lost or is closed, subsequent transaction will no longer be nested because they started in a brand new session. Our internal representation of the nesting shold take this into account

Internally, ArrayStatement expects every row to be represented as an array regardless of the fetch mode, however FetchMode::COLUMN produces one value per row.

The failures are caused by the changes in PHP according to https://wiki.php.net/rfc/notice-for-non-valid-array-container.

The method is not used for anything else than skipping tests for specific drivers. Cross-driver portability should be established by drivers, not outside of them based on their name.

1. Got rid of hard-coded exception mocks in favor of PHPUnit-generated ones where possible.
2. Reworked AbstractDriverTest::testConvertsException() to use a data provider to make testing all types of exceptions independent.
3. Updated PHPUnit since the reworked code relies on sebastianbergmann/phpunit#3604.

on linux running as root.

using params in query cache key generation.