black     - overload the standard black function for delayed transfer functions
bode      - overload the standard bode function for delayed transfer functions
nyquist   - overload the standard nyquist function for delayed transfer functions
calfrqrd  - computes frequency response frequency range discretisation 
            for delayed transfer functions 
repfreqrd - computes frequency response for delayed transfer functions
iodelay   - form delayed transfer function data structure

And overloading functions for delayed transfer function and transfer
function operations (addition concatenations, assignment, reference,
multiplication, ...)
