Clears a numeric handler, such as a
tag_ptr must be a valid pointer to the variable holding the handler.
If the ID is zero then this function does nothing.
clear_func() is called with the ID as a parameter, and the tag is
set to zero.
A macro is also included that allows this function to be used without pointer casts.
Available since: 2.56
This function is not directly available to language bindings.
A pointer to the handler ID.
The data is owned by the caller of the function.
The function to call to clear the handler.