extra_tablenav output for users should have a hook in it

[jakemgold]

In the WP_Users_List_Table class, the extra_tablenav method should really have an action hook in it to allow developers to add additional filters / navigation choices here.

Think of it as the equivalent to the "restrict_manage_posts" action hook for posts.

[jakemgold]

Hook added via patch

[nacin]

"extra_tablenav" is pretty internal. "restrict_manage_users" is consistent and simple.

[Offereins]

For additional filtering we require also the possibility to filter the WP_User_Query object. It seems that only the "pre_user_query" filter is available to do just that. Sadly it's a bridge too far, because the exclude part of the query was already written out by then. Or am I misinformed?

[jakemgold]

Modified name of hook per Nacin's recommendation, also modified the promote user capability check to only wrap the "change role" fields, so that additional filters can be injected here by hooks but not limited to that capability.

[SergeyBiryukov]

Version number indicates when the enhancement was initially suggested.

[johnjamesjacoby]

Moving to 3.5. This is an easy win, and blocking a bbPress 2.2 enhancement. Refreshing patch to match coding standards and prevent needless whitespace on output.

[johnjamesjacoby]

Coding standards improvements

[jakemgold]

Thanks for the tweaks John. I didn't see any differences other than spacing... is that right?

[nacin]

In 22414:

restrict_manage_users action. props jakemgold, johnjamesjacoby. fixes #19295.