wp_login_url() doesn't urlencode() the redirect value

[Viper007Bond]

To reproduce:

1. Log out of your dev blog.
   
2. Visit http://yoursite.com/wp-admin/index.php?foo=bar&test=ing&word=press.
   
3. You will be redirected to http://yoursite.com/wp-login.php?redirect_to=http://yoursite.com/wp-admin/index.php?foo=bar&test=ing&word=press.
   
4. After logging in, you will end up at http://yoursite.com/wp-admin/index.php?foo=bar due to the lack of URL encoding in the redirect_to value.

Attached patch urlencode()'s the value so that the redirect works properly.

[Viper007Bond]

Hmm, perhaps add_query_arg() should urlencode() instead...

[ryan]

(In [11328]) urlencode login redirect. Props Viper007Bond. fixes #9817