Enrich code with comments and explanations

I had a really hard time understanding the provided code. The bison tutorial is not much of a help because it barely provides explanations.

Then I sat down and tried to read into the bison manual and tried to understand what happens.

So this is the outcome of me commenting on everything I did not understand. I would appreciate if you could read through it and tell my if I made any mistakes/ misunderstood some things.

changed the description

mentioned in commit d88358a8

Did the merge by hand (since the "master" branch had advanced quite a bit in the meantime).

So many thanks to Ms. Henning; all of her additions (comments) are now (finally!) fully incorporated.

closed

changed the description