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/libinterp/corefcn/tril.cc	Thu Aug 21 09:46:25 2014 -0700
+++ b/libinterp/corefcn/tril.cc	Thu Aug 21 09:51:18 2014 -0700
@@ -367,7 +367,7 @@
 diagonal; above for positive @var{k} and below for negative @var{k}.\n\
 \n\
 The absolute value of @var{k} must not be greater than the number of\n\
-sub-diagonals or super-diagonals.\n\
+subdiagonals or superdiagonals.\n\
 \n\
 For example:\n\
 \n\