This is a simple one. It does not make sense for an infix language that
uses `-` as a first-class binary (and more importantly, unary) operator.
I liked the idea, but I don't think it was going to work. Plus, I wasn't
using it for builtin functions in the first place, so why keep it
around? Underscores are just fine for our purposes.
Signed-off-by: Alek Ratzloff <alekratz@gmail.com>
