doc: Update more docstrings to have one sentence summary as first line. Reviewed plot/ and gui/ in scripts directory. * scripts/gui/errordlg.m, scripts/gui/helpdlg.m, scripts/gui/inputdlg.m, scripts/gui/listdlg.m, scripts/gui/msgbox.m, scripts/gui/private/__get_funcname__.m, scripts/gui/private/__uiobject_split_args__.m, scripts/gui/questdlg.m, scripts/gui/uigetdir.m, scripts/gui/uigetfile.m, scripts/gui/uiwait.m, scripts/gui/waitbar.m, scripts/gui/warndlg.m, scripts/plot/appearance/annotation.m, scripts/plot/appearance/axis.m, scripts/plot/appearance/box.m, scripts/plot/appearance/caxis.m, scripts/plot/appearance/datetick.m, scripts/plot/appearance/hidden.m, scripts/plot/appearance/legend.m, scripts/plot/appearance/xlim.m, scripts/plot/appearance/ylim.m, scripts/plot/appearance/zlim.m, scripts/plot/draw/area.m, scripts/plot/draw/comet.m, scripts/plot/draw/comet3.m, scripts/plot/draw/contour.m, scripts/plot/draw/contourf.m, scripts/plot/draw/isocolors.m, scripts/plot/draw/isonormals.m, scripts/plot/draw/isosurface.m, scripts/plot/draw/plotmatrix.m, scripts/plot/draw/quiver.m, scripts/plot/draw/quiver3.m, scripts/plot/draw/ribbon.m, scripts/plot/draw/semilogxerr.m, scripts/plot/draw/semilogyerr.m, scripts/plot/draw/sphere.m, scripts/plot/draw/surfl.m, scripts/plot/draw/tetramesh.m, scripts/plot/util/allchild.m, scripts/plot/util/ancestor.m, scripts/plot/util/axes.m, scripts/plot/util/colstyle.m, scripts/plot/util/frame2im.m, scripts/plot/util/gnuplot_binary.in, scripts/plot/util/hgsave.m, scripts/plot/util/im2frame.m, scripts/plot/util/isaxes.m, scripts/plot/util/isfigure.m, scripts/plot/util/linkaxes.m, scripts/plot/util/ndgrid.m, scripts/plot/util/pan.m, scripts/plot/util/print.m, scripts/plot/util/printd.m, scripts/plot/util/private/__add_default_menu__.m, scripts/plot/util/rotate.m, scripts/plot/util/rotate3d.m, scripts/plot/util/saveas.m, scripts/plot/util/struct2hdl.m, scripts/plot/util/subplot.m, scripts/plot/util/zoom.m: Update more docstrings to have one sentence summary as first line.

--- a/scripts/plot/util/allchild.m
+++ b/scripts/plot/util/allchild.m
@@ -21,10 +21,11 @@
 ## Find all children, including hidden children, of a graphics object.
 ##
 ## This function is similar to @code{get (h, "children")}, but also returns
-## hidden objects (HandleVisibility = @qcode{"off"}).  If @var{handles} is a
-## scalar, @var{h} will be a vector.  Otherwise, @var{h} will be a cell
-## matrix of the same size as @var{handles} and each cell will contain a
-## vector of handles.
+## hidden objects (HandleVisibility = @qcode{"off"}).
+##
+## If @var{handles} is a scalar, @var{h} will be a vector.  Otherwise,
+## @var{h} will be a cell matrix of the same size as @var{handles} and each
+## cell will contain a vector of handles.
 ## @seealso{findall, findobj, get, set}
 ## @end deftypefn