maint: Clean up m-files to follow Octave coding conventions. Try to trim long lines to < 80 chars. Use '##' for single line comments. Use '(...)' around tests for if/elseif/switch/while. Abut cell indexing operator '{' next to variable. Abut array indexing operator '(' next to variable. Use space between negation operator '!' and following expression. Use two newlines between endfunction and start of %!test or %!demo code. Remove unnecessary parens grouping between short-circuit operators. Remove stray extra spaces (typos) between variables and assignment operators. Remove stray extra spaces from ends of lines.

--- a/scripts/strings/strjust.m
+++ b/scripts/strings/strjust.m
@@ -104,7 +104,7 @@
 %!        [" a  "; " ab"; "abc "; "abcd"])
 %!assert (strjust (["";""]), "")
 
-%% Test input validation
+## Test input validation
 %!error <Invalid call to strjust> strjust ()
 %!error <Invalid call to strjust> strjust (["a";"ab"], "center", 1)
 %!error <S must be a string> strjust (ones (3,3))