doc: Update more docstrings to have one sentence summary as first line. Reviewed optimization, polynomial, signal script directories. * scripts/optimization/fminbnd.m, scripts/optimization/fminsearch.m, scripts/optimization/fminunc.m, scripts/optimization/fsolve.m, scripts/optimization/fzero.m, scripts/optimization/glpk.m, scripts/optimization/lsqnonneg.m, scripts/optimization/pqpnonneg.m, scripts/optimization/qp.m, scripts/optimization/sqp.m, scripts/polynomial/compan.m, scripts/polynomial/mkpp.m, scripts/polynomial/mpoles.m, scripts/polynomial/pchip.m, scripts/polynomial/poly.m, scripts/polynomial/polyaffine.m, scripts/polynomial/polyder.m, scripts/polynomial/polyeig.m, scripts/polynomial/polyfit.m, scripts/polynomial/polygcd.m, scripts/polynomial/polyint.m, scripts/polynomial/polyout.m, scripts/polynomial/polyval.m, scripts/polynomial/ppder.m, scripts/polynomial/ppint.m, scripts/polynomial/ppjumps.m, scripts/polynomial/ppval.m, scripts/polynomial/residue.m, scripts/polynomial/roots.m, scripts/polynomial/spline.m, scripts/polynomial/splinefit.m, scripts/polynomial/unmkpp.m, scripts/signal/arch_fit.m, scripts/signal/arch_rnd.m, scripts/signal/arma_rnd.m, scripts/signal/autoreg_matrix.m, scripts/signal/bartlett.m, scripts/signal/blackman.m, scripts/signal/detrend.m, scripts/signal/diffpara.m, scripts/signal/durbinlevinson.m, scripts/signal/fftconv.m, scripts/signal/fftfilt.m, scripts/signal/fftshift.m, scripts/signal/filter2.m, scripts/signal/freqz.m, scripts/signal/hamming.m, scripts/signal/hanning.m, scripts/signal/hurst.m, scripts/signal/ifftshift.m, scripts/signal/periodogram.m, scripts/signal/sinc.m, scripts/signal/sinetone.m, scripts/signal/sinewave.m, scripts/signal/spectral_adf.m, scripts/signal/spectral_xdf.m, scripts/signal/spencer.m, scripts/signal/stft.m, scripts/signal/synthesis.m, scripts/signal/unwrap.m, scripts/signal/yulewalker.m: Update more docstrings to have one sentence summary as first line.

--- a/scripts/signal/spectral_xdf.m	Mon May 04 14:22:02 2015 -0700
+++ b/scripts/signal/spectral_xdf.m	Mon May 04 21:50:57 2015 -0700
@@ -20,14 +20,15 @@
 ## @deftypefn  {Function File} {} spectral_xdf (@var{x})
 ## @deftypefnx {Function File} {} spectral_xdf (@var{x}, @var{win})
 ## @deftypefnx {Function File} {} spectral_xdf (@var{x}, @var{win}, @var{b})
-## Return the spectral density estimator given a data vector @var{x},
-## window name @var{win}, and bandwidth, @var{b}.
+## Return the spectral density estimator given a data vector @var{x}, window
+## name @var{win}, and bandwidth, @var{b}.
 ##
-## The window name, e.g., @qcode{"triangle"} or @qcode{"rectangle"} is
-## used to search for a function called @code{@var{win}_sw}.
+## The window name, e.g., @qcode{"triangle"} or @qcode{"rectangle"} is used to
+## search for a function called @code{@var{win}_sw}.
 ##
-## If @var{win} is omitted, the triangle window is used.  If @var{b} is
-## omitted, @code{1 / sqrt (length (@var{x}))} is used.
+## If @var{win} is omitted, the triangle window is used.
+##
+## If @var{b} is omitted, @code{1 / sqrt (length (@var{x}))} is used.
 ## @seealso{spectral_adf}
 ## @end deftypefn