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/image/rgb2ind.m	Mon Feb 23 16:42:25 2015 +0000
+++ b/scripts/image/rgb2ind.m	Mon Feb 23 14:54:39 2015 -0800
@@ -99,7 +99,7 @@
 
 endfunction
 
-%% Test input validation
+## Test input validation
 %!error rgb2ind ()
 %!error rgb2ind (1,2,3,4,5,6,7)
 %!error <RGB> rgb2ind (rand (10, 10, 4))