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/fftfilt.m	Mon May 04 14:22:02 2015 -0700
+++ b/scripts/signal/fftfilt.m	Mon May 04 21:50:57 2015 -0700
@@ -19,18 +19,16 @@
 ## -*- texinfo -*-
 ## @deftypefn  {Function File} {} fftfilt (@var{b}, @var{x})
 ## @deftypefnx {Function File} {} fftfilt (@var{b}, @var{x}, @var{n})
+## Filter @var{x} with the FIR filter @var{b} using the FFT.
 ##
-## With two arguments, @code{fftfilt} filters @var{x} with the FIR filter
-## @var{b} using the FFT.
+## If @var{x} is a matrix, filter each column of the matrix.
 ##
 ## Given the optional third argument, @var{n}, @code{fftfilt} uses the
-## overlap-add method to filter @var{x} with @var{b} using an N-point
-## FFT@.  The FFT size must be an even power of 2 and must be greater than
-## or equal to the length of @var{b}.  If the specified @var{n} does not
-## meet these criteria, it is automatically adjusted to the nearest value
-## that does.
+## overlap-add method to filter @var{x} with @var{b} using an N-point FFT@.
+## The FFT size must be an even power of 2 and must be greater than or equal to
+## the length of @var{b}.  If the specified @var{n} does not meet these
+## criteria, it is automatically adjusted to the nearest value that does.
 ##
-## If @var{x} is a matrix, filter each column of the matrix.
 ## @seealso{filter, filter2}
 ## @end deftypefn