Add constants based on Archimedes' original circle constant

It's a little-known fact that Archimedes' original proof and calculations on the circle constant were not of π, i.e. the ratio of circumference to diameter, but of the ratio of circumference to radius, since the radius is the actual defining characteristic of the circle.  It is therefore perplexing that he would then proceed to use π as the basis for many further proofs, a tradition carried forward by Leonard Euler.

Nonetheless, this isn't a math history lesson, just a very minor patch to rectify said history.  The symbol τ has been promoted in recent years to represent the ratio mentioned (equal to 2π), having a variety of practical, aesthetic, and pedagogical benefits.  If anyone is still curious as to why this is an issue at all, I encourage reading the Tau Manifesto at http://tauday.com, although I would be happy to answer questions myself.