Port WITH-TLS-EA and other remaining FS prefix uses to Windows.

Port WITH-TLS-EA and other remaining FS prefix uses to Windows.

- current-thread-offset-sap

- emit-single-step-test

- Allocation routines

- Disable PSEUDO-ATOMIC on threaded Windows entirely instead of
  changing TLS uses of pseudo-atomic-bits.  We would need a
  temporary register for those changes, and Windows threading is all
  safepoint-based, without the need to support asynchronous signals.

Thanks to Dmitry Kalyanov and Anton Kovalenko.