!!! THIS FUNCTION DOES NOT EXIST ANYMORE !!!
Old documentation :
Merge the filter functions of a specific filter hook with generic filter functions.
It is possible to defined generic filter functions using the filter hook all. These functions are called for every filter tag. This function merges the functions attached to the all hook with the functions of a specific hook defined by $tag.
<?php merge_filters($tag); ?>
merge_filters() is located in