Make lupdate find context from QObject::tr in a wrapper function

/*The inline tr() function sets up the string inside for translation. This is a shorter representation for of the static member QObject::tr () for use outside of a QObject derived class or C-style function. */ 

inline QString tr(const char* sourceText, const char* disambiguation = nullptr, int n = -1)
{
    return QObject::tr (sourceText, disambiguation, n);
}