fix #210 -- implement INDEXES_PAGES support for all pages

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
add a comma to 'old posts page %d'

Makes more sense when it comes to grammar.  Some languages have actually
implemented this in the translations, while others resorted to other, nicer
constructs (like "page %d of old posts").

This might invalidate stuff for people who have changed their locales
manually.  A notice will be added to the changelog.

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
update locales to cover "page %d" and "old posts page %d"

Locales using the Roman, Cyryllic (bg, ru) and Greek (el) scripts
were modified by me to already include the thing, with some help from
Google Translate and wiktionary for 'page'.  However, languages with
other scripts (like fa, jp, ur, zh_CN) were left without a translation.
Note that those translations might not be 100% correct, in which
case I’m terribly sorry.

I also snuggled in an update for the "old posts page %d" string to add
a comma, as per the previous commit (7c756f1).

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>