MFC r271197:
Add more bits for the XSAVE features from CPUID 0xd, sub-function 1
%eax report.  Print the XSAVE features 0xd/1 in the boot banner.
MFC r271206:
Adjust the definition of struct xstate_hdr according to SDM rev. 50.
MFC r271208:
Add a define for index of IA32_XSS MSR.
MFC: r272492

  Merge pc98's machdep.c into i386/i386/machdep.c.