XCF: Support to QImageIOHandler::Size option
requested to merge mircomir/kimageformats:feature/XCF_QImageIOHandler_Size_option_support into master
The handler read the size of the image from the image header, and return this size from option() as a QSize.
QImageReader reader("image.xcf");
auto size = reader.size();
if(size.width() < 30000 && size.height() < 30000) {
auto image = reader.read();
...
}