This is used to remove a POST action that has been previously defined. Each form should have a hidden field titled 'doing'. The value of that field is what will be used to determine which action in %PostingActions will be called (and %PostingActions is built using the RegPostAction subroutine).
Name - This is the name of the action you wish to remove.
This function is not called in the Aneuch source anywhere, however this is being provided as an example for plugin developers.
This will unregister the 'login' POST handler. Any POST data received with the 'doing' field set to 'login' will be discarded.