doc: Periodic spellcheck of the documentation. * doc/interpreter/doccheck/aspell-octave.en.pws: Update Octave-specific Aspell dictionary. * doc/interpreter/contrib.txi, doc/interpreter/errors.txi, doc/interpreter/expr.txi, doc/interpreter/io.txi, doc/interpreter/preface.txi, doc/interpreter/sparse.txi, doc/interpreter/stmt.txi, doc/interpreter/strings.txi, libinterp/corefcn/qz.cc, libinterp/dldfcn/ccolamd.cc, libinterp/dldfcn/fftw.cc, libinterp/interpfcn/graphics.cc, scripts/general/structfun.m, scripts/image/ind2rgb.m, scripts/image/rgb2ind.m, scripts/io/importdata.m, scripts/linear-algebra/duplication_matrix.m, scripts/linear-algebra/housh.m, scripts/miscellaneous/mkoctfile.m, scripts/plot/comet3.m, scripts/plot/gco.m, scripts/plot/legend.m, scripts/plot/print.m, scripts/signal/fftshift.m, scripts/signal/periodogram.m, scripts/sparse/pcg.m, scripts/statistics/tests/f_test_regression.m, scripts/statistics/tests/t_test_regression.m, scripts/strings/strjoin.m, scripts/strings/strsplit.m: Correct spellings or add @nospell macro.

--- a/scripts/general/structfun.m
+++ b/scripts/general/structfun.m
@@ -64,8 +64,8 @@
 ##
 ## @noindent
 ## where there is an additional input argument to @var{errfunc} relative to
-## @var{func}, given by @var{se}.  This is a structure with the elements
-## "identifier", "message" and "index", giving respectively the error
+## @var{func}, given by @nospell{@var{se}}.  This is a structure with the
+## elements "identifier", "message" and "index", giving respectively the error
 ## identifier, the error message, and the index into the input arguments
 ## of the element that caused the error.  For an example on how to use
 ## an error handler, @pxref{docXcellfun, @code{cellfun}}.