doc: Periodic spell check of documentation. * aspell-octave.en.pws: Add new words to custom Octave dictionary. * plot.txi: Correct typo "informations" to "information". * data.cc (Fdiag): Use superdiagonal and subdiagonal instead of hyphenated versions. * tril.cc (Ftril): Use superdiagonal and subdiagonal instead of hyphenated versions. * vech.m: Use superdiagonal instead of supradiagonal. * surfnorm.m: Correct typo "returne" to "returned". * periodogram.m: Use "one-sided" rather than "onesided", "two-sided" rather than "twosided".

--- a/scripts/plot/draw/surfnorm.m
+++ b/scripts/plot/draw/surfnorm.m
@@ -40,7 +40,7 @@
 ## rather than the current axes returned by @code{gca}.
 ##
 ## If output arguments are requested then the components of the normal
-## vectors are returne in @var{nx}, @var{ny}, and @var{nz} and no plot is
+## vectors are returned in @var{nx}, @var{ny}, and @var{nz} and no plot is
 ## made.
 ##
 ## An example of the use of @code{surfnorm} is