This doesn't work for all probers yet, in particular not for the most
generic probers (such as UTF-8) or WINDOWS-1252. These will return NULL.
It's still a good first step.
Right now, it returns the 2-character language code from ISO 639-1. A
using project could easily get the English language name from the
XML/json files provided by the iso-codes project. This project will also
allow to easily localize the language name in other languages through
gettext (this is what we do in GIMP for instance). I don't add any
dependency though and leave it to downstream projects to implement this.
I was also wondering if we want to support region information for cases
when it would make sense. I especially wondered about it for Chinese
encodings as some of them seem quite specific to a region (according to
Wikipedia at least). For the time being though, these just return "zh".
We'll see later if it makes sense to be more accurate (maybe depending
on reports?).
I built models for ISO-8859-1, ISO-8859-4, ISO-8859-9, ISO-8859-13,
ISO-8859-15 and WINDOWS-1252, which all contain Finnish letters.
Nevertheless most texts in these encoding end up the same (same
codepoints for the Finnish glyphs) so I keep only tests for ISO-8859-1
and UTF-8. Models for other encoding may still be useful when processing
texts with some symbols, etc.
