doc: Update docstrings to have one sentence summary as first line. Update scripts in audio, elfun, general, geometry, and image directories. * scripts/audio/@audioplayer/__get_properties__.m, scripts/audio/@audioplayer/audioplayer.m, scripts/audio/@audioplayer/get.m, scripts/audio/@audioplayer/isplaying.m, scripts/audio/@audioplayer/play.m, scripts/audio/@audioplayer/playblocking.m, scripts/audio/@audioplayer/set.m, scripts/audio/@audioplayer/subsasgn.m, scripts/audio/@audioplayer/subsref.m, scripts/audio/@audiorecorder/audiorecorder.m, scripts/audio/@audiorecorder/get.m, scripts/audio/@audiorecorder/getaudiodata.m, scripts/audio/@audiorecorder/getplayer.m, scripts/audio/@audiorecorder/isrecording.m, scripts/audio/@audiorecorder/play.m, scripts/audio/@audiorecorder/record.m, scripts/audio/@audiorecorder/recordblocking.m, scripts/audio/@audiorecorder/set.m, scripts/audio/@audiorecorder/stop.m, scripts/audio/@audiorecorder/subsasgn.m, scripts/audio/@audiorecorder/subsref.m, scripts/audio/lin2mu.m, scripts/audio/mu2lin.m, scripts/audio/record.m, scripts/audio/sound.m, scripts/audio/soundsc.m, scripts/audio/wavread.m, scripts/audio/wavwrite.m, scripts/elfun/cosd.m, scripts/elfun/sind.m, scripts/elfun/tand.m, scripts/general/accumarray.m, scripts/general/accumdim.m, scripts/general/bitcmp.m, scripts/general/bitget.m, scripts/general/bitset.m, scripts/general/blkdiag.m, scripts/general/cart2pol.m, scripts/general/cart2sph.m, scripts/general/cell2mat.m, scripts/general/celldisp.m, scripts/general/chop.m, scripts/general/circshift.m, scripts/general/common_size.m, scripts/general/cplxpair.m, scripts/general/cumtrapz.m, scripts/general/dblquad.m, scripts/general/deal.m, scripts/general/del2.m, scripts/general/display.m, scripts/general/divergence.m, scripts/general/fieldnames.m, scripts/general/flip.m, scripts/general/flipdim.m, scripts/general/fliplr.m, scripts/general/flipud.m, scripts/general/gradient.m, scripts/general/interp3.m, scripts/general/interpft.m, scripts/general/interpn.m, scripts/general/loadobj.m, scripts/general/logspace.m, scripts/general/methods.m, scripts/general/nargchk.m, scripts/general/narginchk.m, scripts/general/nargoutchk.m, scripts/general/nextpow2.m, scripts/general/nthargout.m, scripts/general/num2str.m, scripts/general/pol2cart.m, scripts/general/polyarea.m, scripts/general/postpad.m, scripts/general/prepad.m, scripts/general/profile.m, scripts/general/quadgk.m, scripts/general/quadl.m, scripts/general/quadv.m, scripts/general/randi.m, scripts/general/rat.m, scripts/general/repmat.m, scripts/general/rot90.m, scripts/general/rotdim.m, scripts/general/saveobj.m, scripts/general/shift.m, scripts/general/shiftdim.m, scripts/general/sortrows.m, scripts/general/sph2cart.m, scripts/general/structfun.m, scripts/general/subsindex.m, scripts/general/trapz.m, scripts/general/triplequad.m, scripts/geometry/delaunayn.m, scripts/geometry/dsearch.m, scripts/geometry/dsearchn.m, scripts/geometry/griddata.m, scripts/geometry/griddata3.m, scripts/geometry/griddatan.m, scripts/geometry/inpolygon.m, scripts/geometry/rectint.m, scripts/geometry/tsearchn.m, scripts/geometry/voronoi.m, scripts/geometry/voronoin.m, scripts/help/__unimplemented__.m, scripts/help/doc.m, scripts/help/doc_cache_create.m, scripts/help/get_first_help_sentence.m, scripts/help/help.m, scripts/help/lookfor.m, scripts/help/print_usage.m, scripts/help/type.m, scripts/help/which.m, scripts/image/autumn.m, scripts/image/bone.m, scripts/image/brighten.m, scripts/image/cmpermute.m, scripts/image/colorcube.m, scripts/image/contrast.m, scripts/image/cool.m, scripts/image/copper.m, scripts/image/cubehelix.m, scripts/image/flag.m, scripts/image/gmap40.m, scripts/image/gray.m, scripts/image/gray2ind.m, scripts/image/hot.m, scripts/image/hsv.m, scripts/image/image.m, scripts/image/imagesc.m, scripts/image/imfinfo.m, scripts/image/imformats.m, scripts/image/imread.m, scripts/image/imshow.m, scripts/image/imwrite.m, scripts/image/iscolormap.m, scripts/image/jet.m, scripts/image/lines.m, scripts/image/ntsc2rgb.m, scripts/image/ocean.m, scripts/image/pink.m, scripts/image/prism.m, scripts/image/rainbow.m, scripts/image/rgb2ntsc.m, scripts/image/spinmap.m, scripts/image/spring.m, scripts/image/summer.m, scripts/image/white.m, scripts/image/winter.m: Update docstrings to have one sentence summary as first line. Re-structure to have line lengths <= 80 chars.

--- a/scripts/help/__unimplemented__.m
+++ b/scripts/help/__unimplemented__.m
@@ -18,13 +18,14 @@
 ## <http://www.gnu.org/licenses/>.
 
 ## -*- texinfo -*-
-## @deftypefn {Function File} {@var{txt} =} unimplemented (@var{fcn})
+## @deftypefn {Function File} {@var{txt} =} __unimplemented__ (@var{fcn})
 ## Return specific help text for the unimplemented function @var{fcn}.
+##
 ## This is usually a suggestion for an existing compatible function to use in
 ## place of @var{fcn}.
 ##
-## This function is not called by users, but by the Octave interpreter when
-## it fails to recognize an input string as a valid function name.  See
+## This function is not called by users, but by the Octave interpreter when it
+## fails to recognize an input string as a valid function name.  See
 ## @code{missing_function_hook} for using a different handler for this event.
 ## @seealso{missing_function_hook}
 ## @end deftypefn