[PATCH v4 0/3] MR4987: ntdll: Support generic xstate (part 1).

[Paul Gofman (＠gofman)]

This is a preparation for supporting more xstate features in the contexts.

The remaining parts are:
- support arbitrary xstate in usr1_handler();
- support arbitrary xstate in the server contexts (probably transferring only the present part);
- support arbitrary xstate in context manipulation functions;
- enabling more xstates in system.c and in user shared data.

--
  v4: ntdll: Don't hardcode xstate size in exception stack layout.
      ntdll: Don't hardcode xstate size in syscall frame.
      ntdll: Don't hardcode xstate feature mask.
 
https://gitlab.winehq.org/wine/wine/-/merge_requests/4987