XSB Src (SVN)-old

1. Added commit for backtrackable updates,
so these updates work correctly with all-answer queries
(i.e., not undone due to a fail-loop that is used to obtain all answers).
2. Changed flora_FDB_filename so that the P file will
contain only a base name for the .fdb file.
Instead, flora_load_dyn will attach the directory at the loading time.
This makes .P files location-independent (hopefully)
3. Added while-do and do-until loops.
Require more work: Not yet what is needed, because they commit everything.