Comparison Antlr 3.2 vs Antlr 4.2

This was done with the Xtend debug grammar that is
produced by Xtext. It does not contain any actions.
Antlr 3.2 was used as is, no tweaking. Antlr 4.2 was
tuned according to the suggestions from the Antlr4 book
and tree construction was disabled.

See comments in PoorBenchmark.java.