Fix g++12 warnings

[VitorRamos]

Fix warnings while compiling with g++12

• Initilization order (reorder warnings)
• Implicity copy constructor
• Missing virtual destructor
• Type comparison warnings
• Precedent warning
• Unused variable warnings
• Deprecated warnings

There are a few bug fixes, in the void Frame(unsigned long delta_us) method https://github.com/linthesia/linthesia/blob/1f2701241f8865c2f5c14a97b81ae64884cf0396/src/FrameAverage.cpp#L32 delta_us is unsiged so it can never be less than 0.

Also here in the SongLibState::Init the != is evaluated first so thats not really checking if is a directory or not https://github.com/linthesia/linthesia/blob/1f2701241f8865c2f5c14a97b81ae64884cf0396/src/SongLibState.cpp#L32

[albfan]

Thanks a lot for contributions. All seems great. I will review one by one. Probaby midi in/out will deserve an isolate PR.

How can I simulate that scenario? recover from any midi fail is desired. Stop jack or fluidsynth will show it?