Switch to using FAT classes for advanced settings

- No longer relies on operating system for mounting FAT partition
  when applying 'advanced settings'
- change '__attribute__ ((packed))' to '#pragma pack()' as the
  mingw version we are using for Windows has a bug with the former

src/devicewrapperfatpartition.cpp

@@ -483,7 +483,7 @@ bool DeviceWrapperFatPartition::dirNameExists(const QByteArray dirname)
     while (readDir(&entry))
     {
         if (!(entry.DIR_Attr & ATTR_LONG_NAME)
-                && dirname == QByteArray(entry.DIR_Name, sizeof(entry.DIR_Name)))
+                && dirname == QByteArray((char *) entry.DIR_Name, sizeof(entry.DIR_Name)))
         {
             return true;
         }