[PATCH] Optimize QIconLoader::findIconHelper()

Profiling QIconLoader::findIconHelper() shows that a significant portion of CPU time is being spent in QDir::exists(), which creates a new QFileInfo object for the sole purpose of determining whether the passed-in file path is relative or absolute, and then calls QFile::exists(). In this context, we can just as easily generate the absolute path and call QFile::exists() directly, avoiding the creation of extra QDir and QFileInfo objects.

This change cuts the average CPU time of findIconHelper() in half, and reduces the startup time of Audacious by about 6%.