doc: fix platform notes hierarchy; don't use anydbm session db Linux and Solaris are section headers, but Windows is not. Fix that and move all the windows stuff under the Windows header. Add a section for windows to not use anydbm as the session/otks store. Window only has a dumb dbm written in Python available. gdbm/ndbm compiled backends are not available. So recommend using sqlite or redis for session db if they don't want to spin up mysql/postgresql.