Fix C4189 and C4100 Warnings

C4189 is 'Local variable initialised but not used'
C4100 is 'Unreferenced parameter'

Fixed some other warnings, e.g. about empty if, too.

src/NoteTrack.cpp

@@ -612,7 +612,7 @@ void NoteTrack::Paste(double t, const Track *src)
 
    if ( !bOk )
       // THROW_INCONSISTENCY_EXCEPTION; // ?
-      ;
+      (void)0;// intentionally do nothing
 }
 
 void NoteTrack::Silence(double t0, double t1)