Improved BNode number generator for 2.4 and 2.5+
Improved BNode number generator for 2.4 and 2.5+

_serial_number_generator for BNode had many issues:
1) it used threading.Lock, unnecessarily decreasing performance
2) for Python 2.4, it reseeded random every time instead of only when
PID changed
3) for Python 2.4, random.seed(str) rather than random.seed(long) was
used
4) imports dependent on Python version were far from code that used them

avorio/rdflib,armandobs14/rdflib,ssssam/rdflib,armandobs14/rdflib,ssssam/rdflib,yingerj/rdflib,dbs/rdflib,RDFLib/rdflib,armandobs14/rdflib,ssssam/rdflib,avorio/rdflib,RDFLib/rdflib,yingerj/rdflib,yingerj/rdflib,dbs/rdflib,RDFLib/rdflib,marma/rdflib,avorio/rdflib,avorio/rdflib,RDFLib/rdflib,armandobs14/rdflib,ssssam/rdflib,dbs/rdflib,marma/rdflib,marma/rdflib,yingerj/rdflib,marma/rdflib,dbs/rdflib