doc: Update more docstrings to have one sentence summary as first line. Reviewed specfun, special-matrix, testfun, and time script directories. * scripts/specfun/expint.m, scripts/specfun/isprime.m, scripts/specfun/legendre.m, scripts/specfun/primes.m, scripts/specfun/reallog.m, scripts/specfun/realsqrt.m, scripts/special-matrix/gallery.m, scripts/special-matrix/hadamard.m, scripts/special-matrix/hankel.m, scripts/special-matrix/hilb.m, scripts/special-matrix/invhilb.m, scripts/special-matrix/magic.m, scripts/special-matrix/pascal.m, scripts/special-matrix/rosser.m, scripts/special-matrix/toeplitz.m, scripts/special-matrix/vander.m, scripts/special-matrix/wilkinson.m, scripts/testfun/assert.m, scripts/testfun/demo.m, scripts/testfun/example.m, scripts/testfun/fail.m, scripts/testfun/rundemos.m, scripts/testfun/runtests.m, scripts/testfun/speed.m, scripts/time/asctime.m, scripts/time/calendar.m, scripts/time/clock.m, scripts/time/ctime.m, scripts/time/datenum.m, scripts/time/datestr.m, scripts/time/datevec.m, scripts/time/etime.m, scripts/time/is_leap_year.m, scripts/time/now.m, scripts/time/weekday.m: Update more docstrings to have one sentence summary as first line.

--- a/scripts/special-matrix/hankel.m
+++ b/scripts/special-matrix/hankel.m
@@ -20,13 +20,14 @@
 ## @deftypefn  {Function File} {} hankel (@var{c})
 ## @deftypefnx {Function File} {} hankel (@var{c}, @var{r})
 ## Return the Hankel matrix constructed from the first column @var{c}, and
-## (optionally) the last row @var{r}.  If the last element of @var{c} is
-## not the same as the first element of @var{r}, the last element of
-## @var{c} is used.  If the second argument is omitted, it is assumed to
-## be a vector of zeros with the same size as @var{c}.
+## (optionally) the last row @var{r}.
 ##
-## A Hankel matrix formed from an m-vector @var{c}, and an n-vector
-## @var{r}, has the elements
+## If the last element of @var{c} is not the same as the first element of
+## @var{r}, the last element of @var{c} is used.  If the second argument is
+## omitted, it is assumed to be a vector of zeros with the same size as @var{c}.
+##
+## A Hankel matrix formed from an m-vector @var{c}, and an n-vector @var{r},
+## has the elements
 ## @tex
 ## $$
 ## H(i, j) = \cases{c_{i+j-1},&$i+j-1\le m$;\cr r_{i+j-m},&otherwise.\cr}