Add QFontMetrics::inFont(uint) which checks if a given font supports a specific UCS-4 encoded code point

QFontMetrics::inFont() takes a QChar, which means it only supports characters which are representable by a single unicode point in 16 bits. In order to support all character ranges, we need to implement an overload which takes a UCS-4 encoded code point. Using this, people would be able to make font selection algorithms for unicode ranges that require surrogates in UTF-16.