Fix locale issue on unix systems

Fix locale issue on unix systems

QSystemLocale::query() was missing the LanguageId QueryType. Therefore
QSystemLocale::fallbackLocale() was always used as default language,
which reads environment variables in the order: LC_ALL -> LC_NUMERIC ->
LANG. The correct behaviour is to read LC_ALL -> LC_MESSAGES -> LANG.
This leads to problems for users that want to use english language, but
non-english localization features (date, number formats etc.)

Change-Id: I4310537dac8622a3dd79231fbad58e22f20ca262
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>
Reviewed-by: John Layt <jlayt@kde.org>