doc: Update more docstrings to have one sentence summary as first line. Reviewed libinterp/corefcn directory. * libinterp/corefcn/__ilu__.cc, libinterp/corefcn/balance.cc, libinterp/corefcn/besselj.cc, libinterp/corefcn/betainc.cc, libinterp/corefcn/bitfcns.cc, libinterp/corefcn/bsxfun.cc, libinterp/corefcn/cellfun.cc, libinterp/corefcn/colloc.cc, libinterp/corefcn/conv2.cc, libinterp/corefcn/data.cc, libinterp/corefcn/debug.cc, libinterp/corefcn/defaults.cc, libinterp/corefcn/det.cc, libinterp/corefcn/dirfns.cc, libinterp/corefcn/dlmread.cc, libinterp/corefcn/dot.cc, libinterp/corefcn/eig.cc, libinterp/corefcn/error.cc, libinterp/corefcn/fft2.cc, libinterp/corefcn/fftn.cc, libinterp/corefcn/file-io.cc, libinterp/corefcn/filter.cc, libinterp/corefcn/find.cc, libinterp/corefcn/gammainc.cc, libinterp/corefcn/gcd.cc, libinterp/corefcn/getgrent.cc, libinterp/corefcn/getpwent.cc, libinterp/corefcn/getrusage.cc, libinterp/corefcn/graphics.cc, libinterp/corefcn/help.cc, libinterp/corefcn/hex2num.cc, libinterp/corefcn/input.cc, libinterp/corefcn/inv.cc, libinterp/corefcn/kron.cc, libinterp/corefcn/load-path.cc, libinterp/corefcn/load-save.cc, libinterp/corefcn/lookup.cc, libinterp/corefcn/ls-oct-ascii.cc, libinterp/corefcn/lsode.cc, libinterp/corefcn/lu.cc, libinterp/corefcn/luinc.cc, libinterp/corefcn/mappers.cc, libinterp/corefcn/matrix_type.cc, libinterp/corefcn/max.cc, libinterp/corefcn/md5sum.cc, libinterp/corefcn/mgorth.cc, libinterp/corefcn/nproc.cc, libinterp/corefcn/oct-hist.cc, libinterp/corefcn/ordschur.cc, libinterp/corefcn/pager.cc, libinterp/corefcn/pinv.cc, libinterp/corefcn/pr-output.cc, libinterp/corefcn/pt-jit.cc, libinterp/corefcn/quad.cc, libinterp/corefcn/quadcc.cc, libinterp/corefcn/qz.cc, libinterp/corefcn/rand.cc, libinterp/corefcn/rcond.cc, libinterp/corefcn/regexp.cc, libinterp/corefcn/schur.cc, libinterp/corefcn/sighandlers.cc, libinterp/corefcn/sparse.cc, libinterp/corefcn/spparms.cc, libinterp/corefcn/str2double.cc, libinterp/corefcn/strfind.cc, libinterp/corefcn/strfns.cc, libinterp/corefcn/sub2ind.cc, libinterp/corefcn/svd.cc, libinterp/corefcn/symtab.cc, libinterp/corefcn/syscalls.cc, libinterp/corefcn/sysdep.cc, libinterp/corefcn/time.cc, libinterp/corefcn/toplev.cc, libinterp/corefcn/tril.cc, libinterp/corefcn/tsearch.cc, libinterp/corefcn/typecast.cc, libinterp/corefcn/urlwrite.cc, libinterp/corefcn/utils.cc, libinterp/corefcn/variables.cc, scripts/polynomial/spline.m: Update more docstrings to have one sentence summary as first line.

--- a/libinterp/corefcn/sighandlers.cc	Thu May 07 17:16:36 2015 -0400
+++ b/libinterp/corefcn/sighandlers.cc	Sat May 09 17:19:30 2015 -0700
@@ -1080,11 +1080,13 @@
 @deftypefnx {Built-in Function} {} debug_on_interrupt (@var{new_val}, \"local\")\n\
 Query or set the internal variable that controls whether Octave will try\n\
 to enter debugging mode when it receives an interrupt signal (typically\n\
-generated with @kbd{C-c}).  If a second interrupt signal is received\n\
-before reaching the debugging mode, a normal interrupt will occur.\n\
+generated with @kbd{C-c}).\n\
+\n\
+If a second interrupt signal is received before reaching the debugging mode,\n\
+a normal interrupt will occur.\n\
 \n\
 When called from inside a function with the @qcode{\"local\"} option, the\n\
-variable is changed locally for the function and any subroutines it calls.  \n\
+variable is changed locally for the function and any subroutines it calls.\n\
 The original variable value is restored when exiting the function.\n\
 @seealso{debug_on_error, debug_on_warning}\n\
 @end deftypefn")
@@ -1114,7 +1116,7 @@
 receives a hangup signal.\n\
 \n\
 When called from inside a function with the @qcode{\"local\"} option, the\n\
-variable is changed locally for the function and any subroutines it calls.  \n\
+variable is changed locally for the function and any subroutines it calls.\n\
 The original variable value is restored when exiting the function.\n\
 @end deftypefn")
 {
@@ -1143,7 +1145,7 @@
 receives a terminate signal.\n\
 \n\
 When called from inside a function with the @qcode{\"local\"} option, the\n\
-variable is changed locally for the function and any subroutines it calls.  \n\
+variable is changed locally for the function and any subroutines it calls.\n\
 The original variable value is restored when exiting the function.\n\
 @end deftypefn")
 {