Fix super as statement

Super is a statement, a send really.
Not an expression (as maybe in c++)
The actual implementation will be a bit tricky, like raise, a bit of stack walking, but not impossible. Still, later

lib/vool/statement.rb

@@ -75,6 +75,7 @@ require_relative "class_method_expression"
 require_relative "return_statement"
 require_relative "statements"
 require_relative "send_statement"
+require_relative "super_statement"
 require_relative "variables"
 require_relative "while_statement"
 require_relative "yield_statement"