Generate unique patch filenames

Closes Homebrew/homebrew#11098.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Library/Homebrew/patches.rb

@@ -3,13 +3,14 @@ class Patches
   def initialize patches
     @patches = []
     return if patches.nil?
-
+    n = 0
     normalize_patches(patches).each do |patch_p, urls|
       # Wrap the urls list in an array if it isn't already;
       # DATA.each does each line, which doesn't work so great
       urls = [urls] unless urls.kind_of? Array
-      urls.each_with_index do |url, n|
+      urls.each do |url|
         @patches << Patch.new(patch_p, '%03d-homebrew.diff' % n, url)
+        n += 1
       end
     end
   end