The signal package was loaded when 3.6.2 was installed as:
/usr/share/octave/3.6.2/m/signal/
but there is no hilbert there:
address@hidden:~$ ls /usr/share/octave/3.6.2/m/
signal
arch_fit.m detrend.m fractdiff.m periodogram.m spencer.m
arch_rnd.m diffpara.m freqz.m private stft.m
arch_test.m durbinlevinson.m freqz_plot.m sinc.m synthesis.m
arma_rnd.m fftconv.m hamming.m sinetone.m unwrap.m
autoreg_matrix.m fftfilt.m hanning.m sinewave.m yulewalker.m
bartlett.m fftshift.m hurst.m spectral_adf.m
blackman.m filter2.m ifftshift.m spectral_xdf.m
address@hidden:~$