I need Bison help

Ben: I have a challenge for you.  Put in on your to-do list.  It is in the
main to-do list as "a < b < c".

Python has a cool feature where comparisons can be chained in a human
readable way like 0 < x < 5.  This would be true if x was between 0 and 5.
Right now Prothon (and every other language) would parse this as (0 < x) < 5
which would try to compare the boolean on the left with the integer 5.

I didn't implement it because I couldn't figure out how to get Bison to
parse this.  You are better with Bison than I am so take a stab at it
sometime.