Add support for querying fd-based KVM stats - as introduced by Linux kernel
commit:

cb082bfab59a ("KVM: stats: Add fd-based API to read binary stats data")

This allows the user to analyze the behavior of the VM without access
to debugfs.
Signed-off-by: NMark Kanda <mark.kanda@oracle.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>