apt: udate tarfile + bzip2 libraries

[maphew]

now that setup.exe is no longer susceptible to the dreaded "not a bzip file" error (#101) it's time for apt to do the same, fix this problem:

installing xerces-c-vc9 3.1.1-1
Traceback (most recent call last):
  File "d:\dee\code\o4w\apt\apt.py", line 1029, in <module>
    __main__.__dict__[command] ()
  File "d:\dee\code\o4w\apt\apt.py", line 147, in install
    install_next(missing.keys (), set([]), set([]))
  File "d:\dee\code\o4w\apt\apt.py", line 176, in install_next
    do_install ()
  File "d:\dee\code\o4w\apt\apt.py", line 408, in do_install
    pipe = tarfile.open (ball,'r:bz2')
  File "C:\OSGeo4W\apps\Python25\lib\tarfile.py", line 1166, in open
    return func(name, filemode, fileobj)
  File "C:\OSGeo4W\apps\Python25\lib\tarfile.py", line 1240, in bz2open
    raise ReadError("not a bzip2 file")
tarfile.ReadError: not a bzip2 file

[maphew]

(In [1170]) close #209, error reading certain bzip2 tarfiles

[maphew]

closed by the very simple expedient of allowing tarfile library to open the file transparently instead of specifying the compression method, tarfile.open(foo,'r') instead of tarfile.open(foo,'r:bz2').

4 hours troubleshooting, 2 seconds to fix. ;-)