Eliminate use of `extract()` in `WP_Ajax_Response::add()`. Just set most of the properties to variables to avoid interpolation churn.

See #22400.

Built from https://develop.svn.wordpress.org/trunk@28430


git-svn-id: http://core.svn.wordpress.org/trunk@28257 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Eliminate use of `extract()` in `get_comment_reply_link()`. 

See #22400.

Built from https://develop.svn.wordpress.org/trunk@28431


git-svn-id: http://core.svn.wordpress.org/trunk@28258 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Eliminate use of `extract()` in `wp_dropdown_categories()`. 

See #22400.

Built from https://develop.svn.wordpress.org/trunk@28432


git-svn-id: http://core.svn.wordpress.org/trunk@28259 1a063a9b-81f0-0310-95a4-ce76da25c4cd