Add spellchecker scripts for Octave and run spellcheck of documentation interpreter/doccheck: New directory for spelling/grammar scripts. interpreter/doccheck/README: Instructions for using scripts. interpreter/doccheck/spellcheck: Script to spellcheck a Texinfo file. interpreter/doccheck/aspell.conf: GNU Aspell configuration file for Octave documentation. interpreter/doccheck/aspell-octave.en.pws: Private Aspell dictionary. interpreter/doccheck/add_to_aspell_dict: Script to add new Octave-specific words to private Aspell dictionary. interpreter/octave.texi: New @nospell macro which forces Aspell to ignore the word marked by the macro. interpreter/mk_doc_cache.m: Skip new @nospell macro when building doc_cache.

--- a/scripts/plot/stem3.m
+++ b/scripts/plot/stem3.m
@@ -33,7 +33,7 @@
 ##
 ## @noindent
 ## plots 31 stems with heights from 0 to 6 lying on a circle.  Color 
-## definitions with rgb-triples are not valid!
+## definitions with RGB-triples are not valid!
 ## @seealso{bar, barh, stem, plot}
 ## @end deftypefn