_TrN macro always load catalog translations as singular

[feikname]

Translations using _TrN macro always stay in the singular if loaded from a catalog (e.g. core_locale: pt_br).

The root of the issue are those 2 files:

• Sources/core/string.h
• Sources/core/string.cpp

Specially the GetTextRawPlural() and GetCatalogOfLanguage()->Find() functions.

[mschlumpp]

The parser for the plural expressions seems to be broken, because things like "!=" or ">" won't be parsed.
The reason for this seems to be that ParseLogical is never called. I guess @yvt needs to take a look at this, because I have no idea how the grammar should look like. Additionally the code is really picky about whitespace, because in the case of pt_br it wouldn't even attempt to parse the expression because of the whitespace between "nplurals=2;" and "plural=...".