Handle multiple vocabularies for term reference fields [#2570759]

Hello,

We're using a module called combined_termref to allow multiple vocabularies on a Term Reference field.
When trying to add an exposed filter in a view based on that Term Reference field, only the first vocabulary is handled, the other ones are simply ignored (both in the admin UI and on the view page).

Problem/Motivation

Views cannot handle Term Reference fields that are configured to use multiple vocabularies.

How to reproduce:

Enable Combined Termref module
Create a term reference field and set multiple vocabularies that will supply options
Add an exposed filter on that term reference field
-> Only the first vocabulary is taken into account

Proposed resolution

Patch Views module.

Following function in /modules/taxonomy.views.inc is an example of code that is handling one single vocabualry only (I guess there may be other places where this happens):

/**
 * Implements hook_field_views_data().
 *
 * Views integration for taxonomy_term_reference fields. Adds a term relationship to the default
 * field data.
 *
 * @see field_views_field_default_views_data()
 */
function taxonomy_field_views_data($field) {
  $data = field_views_field_default_views_data($field);
  foreach ($data as $table_name => $table_data) {
    foreach ($table_data as $field_name => $field_data) {
      if (isset($field_data['filter']) && $field_name != 'delta') {
        $data[$table_name][$field_name]['filter']['handler'] = 'views_handler_filter_term_node_tid';
        $data[$table_name][$field_name]['filter']['vocabulary'] = $field['settings']['allowed_values'][0]['vocabulary']; // This instruction only takes the first element (vocabulary) of the array.
      }
    }

    // Add the relationship only on the tid field.
    $data[$table_name][$field['field_name'] . '_tid']['relationship'] = array(
      'handler' => 'views_handler_relationship',
      'base' => 'taxonomy_term_data',
      'base field' => 'tid',
      'label' => t('term from !field_name', array('!field_name' => $field['field_name'])),
    );

  }

  return $data;
}