const math.signMask

4 uses

	math (current package)
		bits.go#L15: 	signMask = 1 << 63
		floor.go#L97: 		bits &= signMask // +-0
		floor.go#L145: 		bits = bits&signMask | uvone // +-1
		floor.go#L148: 		bits &= signMask // +-0