Support id=>name in fields arg of get_terms()

[mikeschinkel]

In trying to use get_terms() I found it didn't support what seemed a common use case; an array where keys were $term->term_id and the values where $term->name.

This patch adds functionailty for a "id=>name" in fields arg of get_terms(). It returns array of term names keyed by the term id.

This path is similar to changeset:12729 by ryan on 2010-Jan-15.

I searched for a similar ticket but didn't find anything recently related.

Add support for "id=>name" in "fields" arg of get_terms() function. Returns array of term names keyed by term id.

Adds a choice of "id=>name" and "id=>slug" for the "fields" argument passed as the 3rd parameter of get_terms() in /wp-includes/taxonomy.php. This choice makes the returned array from get_terms() contains array keys equal to $term->term_id and arrays values equal to $term->name, and array keys equal to $term->slug and arrays values equal to $term->name, respectively.

Ugh. Just as soon as I posted this I realize I really also needed slug=>name. New patch attached.