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/time/clock.m
+++ b/scripts/time/clock.m
@@ -18,10 +18,11 @@
 
 ## -*- texinfo -*-
 ## @deftypefn {Function File} {} clock ()
-## Return the current local date and time as a date vector.  The date vector
-## contains the following fields: current year, month (1-12), day (1-31),
-## hour (0-23), minute (0-59), and second (0-61).  The seconds field has
-## a fractional part after the decimal point for extended accuracy.
+## Return the current local date and time as a date vector.
+##
+## The date vector contains the following fields: current year, month (1-12),
+## day (1-31), hour (0-23), minute (0-59), and second (0-61).  The seconds
+## field has a fractional part after the decimal point for extended accuracy.
 ##
 ## For example:
 ##
@@ -32,8 +33,8 @@
 ## @end group
 ## @end example
 ##
-## The function clock is more accurate on systems that have the
-## @code{gettimeofday} function.
+## @code{clock} is more accurate on systems that have the @code{gettimeofday}
+## function.
 ## @seealso{now, date, datevec}
 ## @end deftypefn