Wrong plural form for e.g. Brazilian Portuguese

[susnux]

The plural form is only looked up by the language part of the locale, e.g. pt for pt_BR.
But for Brazilian Portuguese the plural form is different from Portuguese so it should be first checked if there is a plural function for the whole locale and only if not fallback to the language part.

pt_BR: Plural-Forms: nplurals=2; plural=n>1;
pt: Plural-Forms: nplurals=2; plural=n != 1;