We're using gnulib to get ffs, ffsl, rotl32, count_one_bits,
and count_leading_zeros. Except for rotl32 they can all be
replaced with gcc/clangs builtins. rotl32 is a one-line
trivial function.
Reviewed-by: NJán Tomko <jtomko@redhat.com>
Signed-off-by: NDaniel P. Berrangé <berrange@redhat.com>