posixfile: remove posixfile_nt and fix import bug in windows.py The posixfile_nt class has been superseded by posixfile in osutils.c, which works on Windows NT and above. All other systems get the regular python file class which is assigned to posixfile in posix.py (for POSIX) and in the pure python version of osutils.py (for Win 9x or Windows NT in pure mode).