Using next() for Python 3 compatibility; ordereddict.py converted from DOS to Unix

Converted with `2to3 -w -f next scrapy`, then two places fixed by hand (`assertRaises` in tests)

`xlib/ordereddict.py` was converted by `2to3` from DOS to Unix format. It was the _only_ file in DOS format in project, so I decided to leave it converted (sorry for huge diff). Besides EOL, there is only one trivial change in lines 73-75:

	if last:
		key = next(reversed(self))
	else:
		key = next(iter(self))