Commit
8afde2be995bc0616e25f6959c66dd6bb4e8444f
by marcus.denker#isSelf and #isSuper could always be asked to any AST node. isGlobal and all the others where just defined on RBVariableNode.
This PR unifies the situation:
- make sure that *all* variable tests are defined on RBProgramNode to return false
- simplify some users