libxc: create an initial FPU state for HVM guests

libxc: create an initial FPU state for HVM guests

Xen always set the FPU as initialized when loading a HVM context, so libxc
has to provide a valid FPU context when setting the CPU registers.

This is a stop-gap measure in order to unblock OSSTest Windows 7 failures
while a proper fix for the HVM CPU save/restore is being worked on.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Suggested-by: Jan Beulich <jbeulich@suse.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>