Merge remote-tracking branch 'upstream/DDC-93'

Conflicts:
	doctrine-mapping.xsd
	lib/Doctrine/ORM/Mapping/ClassMetadataFactory.php
	lib/Doctrine/ORM/Mapping/ClassMetadataInfo.php
	lib/Doctrine/ORM/Mapping/Driver/AnnotationDriver.php
	lib/Doctrine/ORM/Mapping/MappingException.php
	lib/Doctrine/ORM/Persisters/BasicEntityPersister.php
	lib/Doctrine/ORM/Persisters/JoinedSubclassPersister.php
	lib/Doctrine/ORM/Tools/SchemaTool.php
	tests/Doctrine/Tests/ORM/Mapping/AbstractMappingDriverTest.php
	tests/Doctrine/Tests/ORM/Mapping/php/Doctrine.Tests.ORM.Mapping.User.php
	tests/Doctrine/Tests/ORM/Mapping/xml/Doctrine.Tests.ORM.Mapping.User.dcm.xml
	tests/Doctrine/Tests/ORM/Mapping/yaml/Doctrine.Tests.ORM.Mapping.User.dcm.yml