-Revert (r26736): reverse_iterators are invalidated when the element next to them is erased (not the element they are pointing to), which makes them unsuitable for ScriptList.

git-svn-id: svn://svn.openttd.org@26741 6aa0318a-3be1-0310-93fa-89fd2396df07
-Doc: Why reverse_iterator is unsuitable for ScriptList iterators

git-svn-id: svn://svn.openttd.org@26742 6aa0318a-3be1-0310-93fa-89fd2396df07