configure: fix Python 3 libdir detection
configure: fix Python 3 libdir detection

No point in handling a 2.5.1 case for Python 3.x.  Use correct Python 3
syntax (print wants parenthesis).  Use existing function
(get_python3_lib doesn't exist).

zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb,zyzyis/monetdb