Reserved names for taxonomies

[scribu]

To prevent issues like #12917, register_taxonomy() should check a list of reserved names, before registering the taxonomy.

[scribu]

First of all, the list should contain the names of registered post types. I know from experience that having the same name for a post type and for a taxonomy leads to trouble.

[mikeschinkel]

Should new reserved names moving forward be prefixed with underscore, maybe?

[SergeyBiryukov]

Related: #18263

[WraithKenny]

I spent some time thinking about this one, and decided it'd make a good Debug Bar extension. There's a hook in register_taxonomy that can be used to setup checks for reserved names. Post type conflicts should be checked later in the execution. Debug Bar would be a great place to output the results.

[helen]

#23213 was marked as a duplicate.

[wonderboymusic]

Duplicate of #11531.

There are a bunch of tickets that all say basically the same thing, closing out this one as dupe

[SergeyBiryukov]

#31155 was marked as a duplicate.