wp-admin should be disallowed as a post slug

[wp_harish]

My wordpress URL structure as follows,

​http://localhost/wordpress/%postname%/

I create post with title wp admin
It generates post url as ​http://localhost/wordpress/wp-admin

Obviously its going to admin login page when i want to see content.. :)

[Clorith]

Should probably also prevent the use of wp-content and wp-includes.

If we're blocking one we might as well block all 3 because it's a given that someone will try to use them.

[swissspidy]

Duplicate of #23478.