#390 OneTopLevelClass check class should not allow specifying tokens

[dhdh]

Currently, for the OneTopLevelClass check, it is possible to specify the tokens on which it is applied class should not allow specifying tokens, e.g.

<module name="OneTopLevelClass">
  <property name="tokens" value="CLASS_DEF,ENUM_DEF,INTERFACE_DEF"/>
</module>

However, this is not allowed for this check, leading to a crash. See also https://github.com/checkstyle/checkstyle/issues/1017. The check always applies to class, enumeration, and interface definitions, and this can not be customized. The Eclipse Checkstyle Plug-in should not allow customizing it in its GUI either.

[Lars Koedderitzsch]

Fixed for 6.8.0 release