Use pgettext for number.ordinal

The problem is that, eg, Russian language have different ordinal suffixes:
```
N	en	ru
------------
0	th	ой
1	st	ый
2	nd	ой
3	rd	ий
4	th	ый
5 	th	ый
6	th	ой
```
So, there is no direct mapping. This fixes problem particularly, but there is still some problems with values > 10, but I don't know how to fix them yet.

It also will be good, if you ask `fr` and `ko` translators to review their translations, since this commit add some fuzzy translations.

See http://www.gnu.org/software/gettext/manual/html_node/Contexts.html to read about `pgettext`. Note, that Python2 don't support `pgettext`, so we reimplement it in GNU gettext compatible way.