Introduce virConnectCompareHypervisorCPU public API
    
    This new API compares the given CPU description with the CPU the
    specified hypervisor is able to provide on the host. It is a more useful
    version of virConnectCompareCPU, which compares the CPU definition with
    the host CPU without considering any specific hypervisor and its
    abilities.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1559832
    https://bugzilla.redhat.com/show_bug.cgi?id=1559835
    
    Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
    Reviewed-by: Ján Tomko <jtomko@redhat.com>
    Reviewed-by: Collin Walling <walling@linux.ibm.com>