Revert #780566 by stella, add drupal_alter() for content_allowed_values lists created by userreference and nodereference, needs more thought.

#780566 by stella, add drupal_alter() for content_allowed_values lists created by userreference and nodereference.

- #649106 by thekevinday: Fix content_copy_form_alter(), where $form_state argument is not passed by reference.

- #585048 Setting "All users" in "User status that can be referenced" option reverts to "Blocked users".

- #572672 by Jan van Diepen - Remove redundant (and bad) inclusion of node/content_types.inc in content_copy_import_form_submit().

- #558420 Accept trimmed titles in nodereference autocomplete validation to prevent title mismatch errors when title ends with space.

- #545942 warning: array_filter() [function.array-filter]: The first argument should be an array in userreference_update_6002().

- #393020 by auth - Fieldgroup data is lost when importing to module provided content type with group info for existing fields.

- #481568 by merlinofchaos - Empty property error when attempting to save a user reference in Panels.

- #231453 Allow fields index their columns. Implemented for reference value column in node and user reference fields. Needs update.php.

- #505278 by Michelle, merlinofchaos - Provide backward compatibility with previous method to build Panels 3 subtype names for fields.

- #505278 by Michelle, merlinofchaos - Provide backward compatibility with previous method to build Panels 3 subtype names for fields.

- #514452 Add new argument $node to content_access() to enhance the context for hook_field_access().

- #414298 by Michelle, merlinofchaos - Follow up to remove fieldgroup.panels.inc (it was moved to panels/content_types).

  Implementation of fieldgroup_view_group() that can be used to render field groups.

  Implementation of fieldgroup_view_group() that can be used to render field groups.