The language_support variable is set to True by default,
and set to False in only 5 engines.
Except the documentation and the /config URL, this variable is not used.
This commit remove the variable definition in the engines, and
set value according to supported_languages length: False when the length is 0,
True otherwise.
Close#2485
check HTTP response:
* detect some comme CAPTCHA challenge (no solving). In this case the engine is suspended for long a time.
* otherwise raise HTTPError as before
the check is done in poolrequests.py (was before in search.py).
update qwant, wikipedia, wikidata to use raise_for_httperror instead of raise_for_status
Add match_language function in utils to match any user given
language code with a list of engine's supported languages.
Also add language_aliases dict on each engine to translate
standard language codes into the custom codes used by the engine.
languages.py can change, so users may query on a language that is not
on the list anymore, even if it is still recognized by a few engines.
also made no and nb the same because they seem to return the same,
though most engines will only support one or the other.
