Eliminate use of `extract()` in `wp_dropdown_pages()`. 

Adds unit tests to: `tests/post/template.php`. 
There was previously only one wimpy assertion for `wp_dropdown_pages()`.
	
See #22400.


git-svn-id: https://develop.svn.wordpress.org/trunk@28399 602fd350-edb4-49c9-b593-d223f7449a82
Add unit tests for `wp_list_pages()`.

Props MikeHansenMe.
See #27326.



git-svn-id: https://develop.svn.wordpress.org/trunk@28400 602fd350-edb4-49c9-b593-d223f7449a82