Typo correction for d-i i18n and l10n Guide

[Tapio Lehtonen <tale@iki.fi>]

7c7
< the spellchecker is a set of scripts which manipulate po files and
---
> The spellchecker is a set of scripts which manipulate po files and
24c24,26
< The statistics page contains the following columns for every language
---
> The statistics page 
> http://d-i.alioth.debian.org/spellcheck/
> contains the following columns for every language
49c51
< translations are spread over many po files, is difficult to make sure
---
> translations are spread over many po files, it is difficult to make sure