added final xor abstract check for enum root class

src/Internal/ConsistencyChecker.php

tests/Basic/accessing-scalar-value.phpt

tests/Basic/autoinstances.phpt

tests/Basic/equals.phpt

tests/Basic/non-strict-value-comparison.phpt

tests/Basic/strict-value-comparison.phpt

tests/Consistency/finalAndAbstractCheck.phpt

tests/Consistency/methodAnnotations.missing.phpt

tests/Consistency/missingInstance.phpt

tests/Example/MigratingLegacyCode/step0.phpt

tests/Example/MigratingLegacyCode/step1.phpt

tests/Example/MigratingLegacyCode/step2.phpt

tests/Example/MigratingLegacyCode/step3.phpt

tests/Reflection/constantNames.phpt

tests/Reflection/getAvailableValues.phpt

...-value-using-static-method-should-throw-an-exception.phpt

...romScalar-non-existing-values-should-throw-exception.phpt

tests/Regression/mixed-key-type-test.phpt