[NTOS]: Implement KiSwapProcess in C.

[NTOS]: Implement KiSwapProcess in C.
[NTOS]: Implement KiIsNpxPresent and KiIsNpxErrataPresent in C. It's much clearer what these are doing now.
[NTOS]: Implement KiFlushNPXState and fix some bugs that were present in the ASM version, such as a wrong NPX state check.
[NTOS]: Implement working intrinsics for fxrstor, fxsave, fnsave and enable them for flushing. We'll update the FPU trap code to use these later.

svn path=/trunk/; revision=45156