Removing annoying NativePhpunitTask from phing and use <exec> to call tests. Include target test in target build again.

DBAL-61 - Merge patch from milokment to align Oracle Transaction behavior to other drivers (Auto-Commit ON when not in an explicit transation).

This reverts commit 3b79401b to allow a sane merge of Juokaz patch.

added supportsReleaseSavepoints(), disabled releasing for Oracle and DB2 (already disabled for MSSQL

disable savepoints by default, added dedicated getter/setter to enable/disable, added exceptions when trying to use savepoints when not supported by the platform