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/hex2dec.m	Mon Feb 23 16:42:25 2015 +0000
+++ b/scripts/strings/hex2dec.m	Mon Feb 23 14:54:39 2015 -0800
@@ -58,7 +58,7 @@
 %!assert (hex2dec (["12b"; "12B"]), [299; 299])
 %!assert (hex2dec ({"A1", "1A"}), [161; 26])
 
-%%Test input validation
+## Test input validation
 %!error hex2dec ()
 %!error hex2dec (1)
 %!error hex2dec ("1", 2)