x86: ioperm user_regset

This adds a user_regset type for the x86 io permissions bitmap.
This makes it appear in core dumps (when ioperm has been used).
It will also make it visible to debuggers in the future.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
[conflict resolutions: Signed-off-by: Ingo Molnar <mingo@elte.hu> ]