Typical execution extension

[Dionysis Zindros]

Extend the typical execution definitions from backbone to include random variables X^\mu, Y^\mu and Z^\mu. These denote respectively honest success, honest unique success and adversarial success in the attempt to produce a \mu-level superblock in a given round or range of rounds. Due to Chernoff bounds, they will be close to their means for small enough \mu. The maximum mu for which this holds intuitively is that which corresponds to the topmost chain of at least m blocks, but this is self-referential. Instead, it can be said that that \mu is simply lg|C| - lgm, but this may not be sufficient for the formal proof. For this definition, it may be sufficient to let \mu be a free parameter.