Update _functions.php to map to correct custom post type tables

With WordPress I can associate any entity meta type to a different post table - for example ...

    global $wpdb;
    $wpdb->cptmeta = "{$wpdb->prefix}cptmeta";

Right now in `fields/_functions.php  acf_field_functions@update_value` there is `update_metadata('post', ...` which is problematic in my case because I mapped by custom post type meta to a different table. As a result WordPress tries to map to `cptmetapostmeta` which doesn't follow the appropriate naming structure.