benchmark/app_aobench.rb: complete commented code to write the image to a file

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66900 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

benchmark/app_aobench.rb

@@ -282,9 +282,11 @@ end
 
 alias printf_orig printf
 def printf *args
+  # $fp.printf(*args)
 end
 
 # File.open("ao.ppm", "w") do |fp|
+  # $fp = fp
   printf("P6\n")
   printf("%d %d\n", IMAGE_WIDTH, IMAGE_HEIGHT)
   printf("255\n")