_field_sql_storage_indexname() should not prefix the index name with the table name

using postgresql i encountered an error about index name truncated for being too long
and resulted in a failure to create a table for index naming collision
i found that both _field_sql_storage_indexname and http://api.drupal.org/api/drupal/includes!database!pgsql!schema.inc/function/DatabaseSchema_pgsql%3A%3A_createIndexSql/7">_createIndexSql prefixes the name with the table name

i believe the solution is for _field_sql_storage_indexname to simply return $index