doc: Periodic grammarcheck of documentation. * doc/interpreter/contrib.txi, doc/interpreter/expr.txi, doc/interpreter/func.txi, doc/interpreter/linalg.txi, doc/interpreter/plot.txi, libinterp/corefcn/data.cc, libinterp/corefcn/debug.cc, libinterp/corefcn/graphics.cc, libinterp/corefcn/help.cc, libinterp/corefcn/load-save.cc, libinterp/corefcn/profiler.cc, libinterp/corefcn/syscalls.cc, libinterp/corefcn/utils.cc, libinterp/corefcn/variables.cc, libinterp/dldfcn/__init_fltk__.cc, scripts/general/deal.m, scripts/help/__gripe_missing_component__.m, scripts/miscellaneous/desktop.m, scripts/pkg/private/default_prefix.m, scripts/plot/appearance/__getlegenddata__.m, scripts/plot/util/pan.m, scripts/plot/util/rotate.m, scripts/plot/util/rotate3d.m, scripts/plot/util/zoom.m, scripts/signal/periodogram.m, scripts/specfun/factor.m, scripts/specfun/primes.m, scripts/statistics/base/lscov.m, scripts/testfun/private/compare_plot_demos.m, scripts/testfun/private/dump_demos.m, scripts/testfun/private/html_compare_plot_demos.m, scripts/testfun/test.m: Periodic grammarcheck of documentation.

--- a/scripts/testfun/private/compare_plot_demos.m
+++ b/scripts/testfun/private/compare_plot_demos.m
@@ -24,7 +24,7 @@
 ## html comparison of the plot demos for each of Octave's graphics toolkits.
 ##
 ## An m-file named @file{dump_plots.m} will be created in the current working
-## directory. This function will be used to render and save the plot demo
+## directory.  This function will be used to render and save the plot demo
 ## images.
 ##
 ## If they do not already exist, directories for each available graphics