Type checker should warn for convoluted references.

Users should get a warning when they use convoluting references, such when relative/absolute/root names are used instead of identifiers.

For example, in the following example, all three event references should get a warning, because identifier e should be used.

automaton p:
  event e;
  location:
    initial;
    edge ^p.e;
    edge .p.e;
    edge p.e;
end

as a warning we may use:

• "Convoluted reference to local variable. Use "<ref>" instead."

Provide for <ref> the reference to use, the name of the variable, escaped in case it is a keyword.