It's basically pop_dom_nodes() without the search part and is now used as a
backend in pop_dom_nodes(). Use it in parse_sgml_document() to avoid two
DOM stack searches in a row.
There already was one work-around in the code related to clearing of the
state data after popping. Instead of storing a pointer to the state data in
the state we now store the depth of the state (in the stack) and use a
macro to access the state data. The bug occurred when reallocating the
stack state objects and the stack data pointers wasn't updated to point to
the newly allocated data.
This is really a much more appropriate word since it never ended up being
more than just a stack. The rename also changes the symbol names to use the
much shorter "stack".
