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/hilb.m	Sun May 03 15:36:23 2015 -0700
+++ b/scripts/special-matrix/hilb.m	Sun May 03 17:00:11 2015 -0700
@@ -18,8 +18,9 @@
 
 ## -*- texinfo -*-
 ## @deftypefn {Function File} {} hilb (@var{n})
-## Return the Hilbert matrix of order @var{n}.  The @math{i,j} element
-## of a Hilbert matrix is defined as
+## Return the Hilbert matrix of order @var{n}.
+##
+## The @math{i,j} element of a Hilbert matrix is defined as
 ## @tex
 ## $$
 ## H(i, j) = {1 \over (i + j - 1)}
@@ -34,9 +35,9 @@
 ## @end ifnottex
 ##
 ## Hilbert matrices are close to being singular which make them difficult to
-## invert with numerical routines.
-## Comparing the condition number of a random matrix 5x5 matrix with that of
-## a Hilbert matrix of order 5 reveals just how difficult the problem is.
+## invert with numerical routines.  Comparing the condition number of a random
+## matrix 5x5 matrix with that of a Hilbert matrix of order 5 reveals just how
+## difficult the problem is.
 ##
 ## @example
 ## @group