Add comment on coefs symmetry.

applications/lofar2/model/pfb_bunton_annotated/Gen_filter12.m

@@ -77,6 +77,8 @@ title ('Sum of correlator responses for Bin 0 and 1')
 % 2304, using Q = 12. The number of FFT blocks remains Ntaps = 12, because
 % the shape of cl is the same as for c. The FFT block size now becomes Nfft =
 % Kfft * Q = 16 * 12 = 192.
+% Using Q > 1 does cause the FIR filter to become slightly asymmetrical, so
+% the group delay is not exactly constant (Ncoefs - 1) / 2.
 Q = 12;
 % Y = interpft(X, N) returns a vector Y of length N obtained by interpolation
 % in the Fourier transform of X.