correct bug #3

ltfatpy/fourier/pderiv.py

ltfatpy/fourier/pgauss.py

ltfatpy/fourier/pherm.py

ltfatpy/fourier/psech.py

ltfatpy/gabor/dgt.py

ltfatpy/gabor/dgtlength.py

ltfatpy/gabor/dgtreal.py

ltfatpy/gabor/gabdual.py

ltfatpy/gabor/gabframediag.py

ltfatpy/gabor/gabimagepars.py

ltfatpy/gabor/gabphasegrad.py

ltfatpy/gabor/gabtight.py

ltfatpy/gabor/gabwin.py

ltfatpy/gabor/idgt.py

ltfatpy/gabor/idgtreal.py

ltfatpy/gabor/instfreqplot.py

ltfatpy/gabor/phaselock.py

ltfatpy/gabor/phaseplot.py

ltfatpy/gabor/phaseunlock.py

ltfatpy/gabor/plotdgt.py