XSB Src (SVN)-old

Generalized the way the .xsb/ dir is determined. Now:

o use the value of environment $XSB_USER_AUXDIR if defined and not ""
o use $HOME/.xsb, if HOME is defined
o use $USERHOME/.xsb, if USERHOME ...
o use XSBinstalldir/.xsb

This generalization is needed when XSB is used by a servlet. Eg, tomcat runs as a nologin user and its $HOME is owned by root. So, no way to run XSB this way. With $XSB_USER_AUXDIR, one can point to a dir owned by user 'tomcat'.
Dunno how this kind of services are done on windoze, but probably useful there as well.

fixed some incorrect comments
also incorrect refs to .xsbrc in the manual

Created a new p2p_attvar to replace p2p_arg(_,0)

Add simple predicate to gensym to help logging. Slightly improved performance of unnumbervars, which is heavily used in prolog_db.

Comment out unnecessary import to avoid warning.

Commented out unnecessary import to eliminate warning.

better comments for GET_TMP_FILENAME

revived the old Teri's attempt to reimplement tempnam on linux/mac, but made it compatible with the old tempnam.
Kept the windows version as before, as windows does not complain about this function.

Forgot to run bibtex

Updated PITA documentation.