Use wrapping operations for bit-level functions
Use wrapping operations for bit-level functions

This handles a underflow panic on round_up_to_power_of_two(0).

aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,studoot/rustfmt,graydon/rust,graydon/rust,SingingTree/rustfmt,rust-lang/rustfmt,aidancully/rust,Emilgardis/rustfmt,SingingTree/rustfmt,aidancully/rust,flutterhash/rustfmt,graydon/rust,rust-lang/rustfmt,Emilgardis/rustfmt,graydon/rust,aidancully/rust,studoot/rustfmt