Don't query against entire users table in wp_dropdown_users()

[ryan]

To be MU friendly, wp_dropdown_users() should use get_users_of_blog() or a like query.

[nacin]

Pretty sure we'd need $wpdb->get_blog_prefix in non-MU WP to be able to add $blog_id as an argument. First patch was incomplete in that regard, I thought I had pulled the $blog_id code before patching.

[nacin]

Missing semi-colon.

[ryan]

Thanks for the patch. It looks good, but let's postpone this to 3.0.

[nacin]

Patch still applies clean (thought offset) on r12962.

[nacin]

(In [13122]) Don't query against entire users table in wp_dropdown_users() to be multisite friendly. Fixes #11086

[nacin]

(In [13123]) s/$blog/$blog_id/ as an argument in wp_dropdown_users(), for consistency, see #11086