• Allow NULL in expressions.
• Downgraded PHPUnit to 4.8. Removed old PHP versions.
• Updated PHPUnit to 5.1 and fixed some of the tests.
• Added UNION ALL as a type of UNION.
• Expressions are permitted in SET operations.
• Added STRAIGHT_JOIN as a known type of join.
• Added missing definitions for MATCH and AGAINST.
• Added missing statement (FLUSH and DEALLOCATE).