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/ctime.m	Sun May 03 15:36:23 2015 -0700
+++ b/scripts/time/ctime.m	Sun May 03 17:00:11 2015 -0700
@@ -20,7 +20,9 @@
 ## @deftypefn {Function File} {} ctime (@var{t})
 ## Convert a value returned from @code{time} (or any other non-negative
 ## integer), to the local time and return a string of the same form as
-## @code{asctime}.  The function @code{ctime (time)} is equivalent to
+## @code{asctime}.
+##
+## The function @code{ctime (time)} is equivalent to
 ## @code{asctime (localtime (time))}.  For example:
 ##
 ## @example