Log Message:
math/dragonbox: import dragonbox-1.1.3

This library is a reference implementation of Dragonbox in C++.

Dragonbox is a float-to-string conversion algorithm based on a
beautiful algorithm Schubfach, developed by Raffaello Giulietti in
2017-2018. Dragonbox is further inspired by Grisu and Grisu-Exact.