Fix "Error: src/lib/cpml/modules/_private_utils.lua:8: attempt to index
global 'utils' (a nil value)"
Looks like when round was moved to _private_utils, this didn't get
replaced. There is no utils defined and utils.round just points to
private.round.
Add a test. This never triggered test failures because test don't pass
precision.
Test
A love2d program with main.lua:
local Vec2 = require "cpml.modules.vec2"
local v = Vec2(1.234, 3.5326)
print(v:round(0.1))
