Fixed unreviewed commit, which might lead to hard-to-spot errors
The last change assumed that "nls_language" can be hard-wired to
contain most 5 characters. While this not backed by the OpenACS data
model, the standard (RFC 5646) explicitly states that there is no
upper limit on the size of language tags. The tree letter language
codes have been standard since 2001 (RFC 4646).
The change accepts now all defined locales. When the specified locale
is not enabled, it provides a log notice, when the locale is not
defined at all, it provides a warning and falls back to "en_US".