Support OCI8 statements crossing transactions [DBAL-202]

Bug Fix: yes
Feature addition: no
Backwards compatibility break: no
[![Build Status](https://secure.travis-ci.org/dpb587/dbal.png?branch=ticket-dbal-202)](http://travis-ci.org/dpb587/dbal)

Scenario is documented in JIRA [DBAL-202](http://www.doctrine-project.org/jira/browse/DBAL-202). Basically in oci8 if you prepare a statement outside of a transaction, start a transaction, execute the statement, rollback the transaction - the statement will still have been executed. Whether it's the correct behavior or not, it seems like it should match PDO's behavior.

This implementation affects the API, so it should probably be carefully reviewed.

A separate test script is available at [https://gist.github.com/2515100](gist.github.com/2515100).

    $ php -v ; php --re oci8 | head -1
    PHP 5.3.3-7+squeeze3 with Suhosin-Patch (cli) (built: Jun 28 2011 08:24:40) 
    Copyright (c) 1997-2009 The PHP Group
    Zend Engine v2.3.0, Copyright (c) 1998-2010 Zend Technologies
        with Xdebug v2.1.1, Copyright (c) 2002-2011, by Derick Rethans
        with Suhosin v0.9.32.1, Copyright (c) 2007-2010, by SektionEins GmbH
    Extension [ <persistent> extension #52 oci8 version 1.4.2 ] {
    $ phpunit -c oci8.phpunit.xml.dist tests/Doctrine/Tests/DBAL/Driver/OCI8/OCI8StatementTest.php
    PHPUnit 3.5.13 by Sebastian Bergmann.

    ..

    Time: 0 seconds, Memory: 7.50Mb

    OK (2 tests, 2 assertions)
    $ phpunit -c oci8.phpunit.xml.dist tests/Doctrine/Tests/DBAL/Functional/Ticket/DBAL202Test.php
    PHPUnit 3.5.13 by Sebastian Bergmann.

    ..

    Time: 7 seconds, Memory: 9.50Mb
    OK (2 tests, 6 assertions)

I had to drop the the following tests to run through the oracle test suite (seemed like my test user didn't have enough permissions for the temp db tests), but all other tests pass.

    $ rm tests/Doctrine/Tests/DBAL/Functional/TemporaryTableTest.php
    $ rm tests/Doctrine/Tests/DBAL/Functional/TableGeneratorTest.php # see pull 136
    $ rm tests/Doctrine/Tests/DBAL/Functional/Schema/OracleSchemaManagerTest.php
    $ phpunit -c oci8.phpunit.xml.dist
    PHPUnit 3.5.13 by Sebastian Bergmann.

    ...............................................................  63 / 747 (  8%)
    .......SSSS.....S........S......................S...........S.. 126 / 747 ( 16%)
    .............................SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS 189 / 747 ( 25%)
    SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS 252 / 747 ( 33%)
    SSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSSS.............S........ 315 / 747 ( 42%)
    ...S...S...SSS................................................. 378 / 747 ( 50%)
    ............................................................... 441 / 747 ( 59%)
    .....SSS....................................................... 504 / 747 ( 67%)
    ............................................................... 567 / 747 ( 75%)
    ..............S................................................ 630 / 747 ( 84%)
    ............................................................... 693 / 747 ( 92%)
    ......................................................

    Time: 33 seconds, Memory: 46.00Mb

    OK, but incomplete or skipped tests!
    Tests: 747, Assertions: 1145, Skipped: 156.