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/autoreg_matrix.m	Mon May 04 14:22:02 2015 -0700
+++ b/scripts/signal/autoreg_matrix.m	Mon May 04 21:50:57 2015 -0700
@@ -18,12 +18,14 @@
 
 ## -*- texinfo -*-
 ## @deftypefn {Function File} {} autoreg_matrix (@var{y}, @var{k})
-## Given a time series (vector) @var{y}, return a matrix with ones in the
-## first column and the first @var{k} lagged values of @var{y} in the
-## other columns.  I.e., for @var{t} > @var{k}, @code{[1,
-## @var{y}(@var{t}-1), @dots{}, @var{y}(@var{t}-@var{k})]} is the t-th row
-## of the result.  The resulting matrix may be used as a regressor matrix
-## in autoregressions.
+## Given a time series (vector) @var{y}, return a matrix with ones in the first
+## column and the first @var{k} lagged values of @var{y} in the other columns.
+##
+## In other words, for @var{t} > @var{k},
+## @code{[1, @var{y}(@var{t}-1), @dots{}, @var{y}(@var{t}-@var{k})]} is the
+## t-th row of the result.
+##
+## The resulting matrix may be used as a regressor matrix in autoregressions.
 ## @end deftypefn
 
 ## Author: KH <Kurt.Hornik@wu-wien.ac.at>