Fix various string formatting warnings

[turboencabulator]

This fixes a handful of warnings where the format strings disagree with the variable type, plus replacing a deprecated function.

As an aside, Qt's string handling is really inconsistent so there are 4 different styles here. QString::arg is the preferred type-safe way to do string formatting, except it doesn't support const char * and you have to use QString::asprintf. qDebug supports C-style format strings and the safer but uglier C++-style stream insertion, but qFatal only supports the format strings.