Implementation for 'IsNot'-Comparison

See PR (https://github.com/doctrine/collections/pull/11)

This is the required implementation for 'IsNotNull'-Filters in Collection-Filtering.
Changed to IS_NOT
Merge branch 'master' of https://github.com/pmattmann/doctrine2 into master2

Conflicts:
	lib/Doctrine/ORM/Persisters/BasicEntityPersister.php
	tests/Doctrine/Tests/ORM/Persisters/BasicEntityPersisterTypeValueSqlTest.php