xen: update interface headers

[ehem_freebsd_m5p.com]

Summary

This is a verbatim copy of the public headers from Xen commit
747424c664bb164a04e7a9f2ffbf02d4a1630d7d (post 4.15).

Notably for FreeBSD this includes fixes of ARM64 which make them
compatible with FreeBSD's kernel build environment (previously had
typeof() instead of typeof()).

[royger]

I usually import the whole headers at once in order to keep them in sync with specific versions. I would be fine if you just pick the whole contents of the public/ folder after your change and dump it directly on FreeBSD.

[ehem_freebsd_m5p.com]

Updating to reflect plans. These headers may well deserve further update later.

[ehem_freebsd_m5p.com]

This was updated to reflect more up to date Xen public headers. One thing I noted during full update, the "gcov.h" header seems to have been removed some time ago. The last update copied newer headers on top, but missed removing (likely to how git functions).

I'm unsure of the time frame for when this gets put in.

I suggest these should really move to sys/contrib/xen. There are two reasons for this. First, these are purely maintained outside of FreeBSD. Second, this avoids people doing cleanup on these headers and hopefully suggests updates should go upstream. I've got things in place to do this, just say the word.

[ehem_freebsd_m5p.com]

Nuking this since this version is obsolete and the headers got updated.