update doc with native-complex idiom

Author: mohawk2

README.pod

@@ -64,8 +64,7 @@ PDL::FFTW3 - PDL interface to the Fastest Fourier Transform in the West v3
 
  # compute the correlation
  my $F12  = rfft1( cat($y1,$y2) );
- my $corr = irfft1( Cmul(      $F12(:,:,(1)),
-                            Cconj $F12(:,:,(0)) ) );
+ my $corr = irfft1( $F12(:,(1)) * $F12(:,(0))->conj );
  # and find the peak
  say maximum_ind($corr);