itertools.izip_longest is not in Python 3

git-svn-id: http://svn6.assembla.com/svn/pyfits/branches/3.1-stable@2691 ed100bfc-0583-0410-97f2-c26b58777a21
If the provided 'fileobj' is actually just a string (for a file path) it should be treated as 'closed'

Conflicts:

	lib/pyfits/hdu/hdulist.py

git-svn-id: http://svn6.assembla.com/svn/pyfits/branches/3.1-stable@2695 ed100bfc-0583-0410-97f2-c26b58777a21
Add izip_longest implementation for python 2.5

git-svn-id: http://svn6.assembla.com/svn/pyfits/branches/3.1-stable@2705 ed100bfc-0583-0410-97f2-c26b58777a21