v0.2.0

• Make _IOC generic over the ioctl argument type.

  • This makes _IOC easier to use by no longer requiring virtually every use of it to be followed-up with .with_arg().

• _IOC_x constants are now newtypes.

  • This makes it harder to pass invalid values to _IOC.
  • Specifically, _IOC_NONE is 0 on x86, but non-zero on other architectures, posing a portability hazard if 0 is passed as a literal by mistake.