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/detrend.m	Mon May 04 14:22:02 2015 -0700
+++ b/scripts/signal/detrend.m	Mon May 04 21:50:57 2015 -0700
@@ -24,13 +24,12 @@
 ## If @var{x} is a matrix, @code{detrend (@var{x}, @var{p})} does the same
 ## for each column in @var{x}.
 ##
-## The second argument is optional.  If it is not specified, a value of 1
-## is assumed.  This corresponds to removing a linear trend.
+## The second argument @var{p} is optional.  If it is not specified, a value of
+## 1 is assumed.  This corresponds to removing a linear trend.
 ##
 ## The order of the polynomial can also be given as a string, in which case
-## @var{p} must be either @qcode{"constant"} (corresponds to
-## @code{@var{p}=0}) or
-## @qcode{"linear"} (corresponds to @code{@var{p}=1}).
+## @var{p} must be either @qcode{"constant"} (corresponds to @code{@var{p}=0})
+## or @qcode{"linear"} (corresponds to @code{@var{p}=1}).
 ## @seealso{polyfit}
 ## @end deftypefn