doc: Tweak docstrings of functions changed for Texinfo 5.0 compatibility. * scripts/audio/wavread.m, scripts/miscellaneous/getappdata.m, scripts/miscellaneous/license.m, scripts/miscellaneous/ver.m, scripts/plot/daspect.m, scripts/plot/graphics_toolkit.m, scripts/plot/pbaspect.m, scripts/polynomial/splinefit.m, scripts/set/union.m, scripts/signal/freqz.m: Improve docstring wording.