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/stft.m	Mon May 04 14:22:02 2015 -0700
+++ b/scripts/signal/stft.m	Mon May 04 21:50:57 2015 -0700
@@ -47,14 +47,13 @@
 ## @var{win_size} = 80, @var{inc} = 24, @var{num_coef} = 64, and
 ## @var{win_type} = 1.
 ##
-## @code{@var{y} = stft (@var{x}, @dots{})} returns the absolute values
-## of the Fourier coefficients according to the @var{num_coef} positive
-## frequencies.
+## @code{@var{y} = stft (@var{x}, @dots{})} returns the absolute values of the
+## Fourier coefficients according to the @var{num_coef} positive frequencies.
 ##
-## @code{[@var{y}, @var{c}] = stft (@code{x}, @dots{})} returns the
-## entire STFT-matrix @var{y} and a 3-element vector @var{c} containing
-## the window size, increment, and window type, which is needed by the
-## @code{synthesis} function.
+## @code{[@var{y}, @var{c}] = stft (@code{x}, @dots{})} returns the entire
+## STFT-matrix @var{y} and a 3-element vector @var{c} containing the window
+## size, increment, and window type, which is needed by the @code{synthesis}
+## function.
 ## @seealso{synthesis}
 ## @end deftypefn