Fix xsaves and xsaves64 tests

[gnzlbg]

So after #211 is merged, this is the current state of affairs:

• xsaves,xsaves64, and xsetbv cannot be easily tested because they require privileged mode
• all other xsave intrinsics are tested in i586, i686, and x86_64
• the following intrinsics fail on travis when using Intel's Software Development Emulator version: 8.12.0-2017-10-23, these are disabled from that test run using #[cfg(not(feature = "intel_sde"))]:
  • i586::xsaveopt and x86_64::xsaveopt64
  • i586::xsavec and x86_64::xsavec64
  • x86_64::xsave64