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/libinterp/corefcn/utils.cc
+++ b/libinterp/corefcn/utils.cc
@@ -1519,9 +1519,10 @@
 
 DEFUN (isstudent, args, ,
        "-*- texinfo -*-\n\
-@deftypefn  {Built-in Function} {} isstudent ()\n\
-Return true if running in the student edition of Matlab.\n\
-Always return false in Octave.\n\
+@deftypefn {Built-in Function} {} isstudent ()\n\
+Return true if running in the student edition of @sc{matlab}.\n\
+\n\
+@code{isstudent} always returns false in Octave.\n\
 \n\
 @seealso{false}\n\
 @end deftypefn")
@@ -1533,6 +1534,7 @@
 }
 
 /*
-%!assert (isstudent (), false);
-%!error isstudent (1);
+%!assert (isstudent (), false)
+
+%!error isstudent (1)
 */