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/tracks/ui/TimeShiftHandle.cpp

@@ -536,6 +536,8 @@ namespace {
       const ViewInfo &viewInfo, wxCoord xx, ClipMoveState &state,
       double tolerance, double &desiredSlideAmount )
    {
+      (void)xx;// Compiler food
+      (void)viewInfo;// Compiler food
       bool ok = true;
       double firstTolerance = tolerance;