Errors in itertools.po

There is an English sentence remaining: "elements of seq where pred(elem) is false". This seems weird to me as I've already translated this string. 
Also, every time a paragraph is started with " ::" at the end of a line, the leading ":" is missing. It should be " : ::" every time, else the colon will not print.

I'll make a pull request when I can if nobody can fix this quicker than I can. 