GPodDevice: Add ALAC to supported file types for iPods

There are some iPods which do not support ALAC, but they are quite rare. Anything 3rd gen
and newer, which most people are likely to be using, will work if upgraded to the latest
firmware (they probably are already on it...)

src/device/gpoddevice.cpp

@@ -409,5 +409,6 @@ bool GPodDevice::FinishDelete(bool success, QString &error_text) {
 bool GPodDevice::GetSupportedFiletypes(QList<Song::FileType> *ret) {
   *ret << Song::FileType::MP4;
   *ret << Song::FileType::MPEG;
+  *ret << Song::FileType::ALAC;
   return true;
 }