r: specify rule sets for epsilon elimination

[stefan11]

Section 7.2
It would be very useful to present this example of a grammar
transformation with explicit rule sets, writing out the modified rule
sets after each step and assigning them names. The discussion would be
much easier to follow for readers without prior experience with these
techniques, without getting much longer.

So we would get:
R_1 = {rule1, rule2, ..., rule_n}
R_2 = new set of rules
...
R_n = final set of rules

In its present form, the section feels like an exercise for the reader
to figure it all out from the hints in the text.

OK. Good suggestion.

To do.