Add an alias for Deprecated to be compatible with PHP5.6

tests/phpunit_aliases.php

@@ -7,4 +7,5 @@ if (class_exists('PHPUnit_Runner_Version')) {
     class_alias('PHPUnit_Framework_Test', 'PHPUnit\Framework\Test');
     class_alias('PHPUnit_Framework_AssertionFailedError', 'PHPUnit\Framework\AssertionFailedError');
     class_alias('PHPUnit_Framework_TestSuite', 'PHPUnit\Framework\TestSuite');
+    class_alias('PHPUnit_Framework_Error_Deprecated', 'PHPUnit\Framework\Error\Deprecated');
 }