Fix Windows build

vs2013/5 do not support defaulted move constructed, so made it explicit.

src/Snap.cpp

@@ -33,6 +33,12 @@ TrackClip::TrackClip(Track *t, WaveClip *c)
    clip = c;
 }
 
+#ifndef __AUDACITY_OLD_STD__
+TrackClip::TrackClip(TrackClip&& tc)
+   : track{tc.track}, origTrack{tc.origTrack}, dstTrack{tc.dstTrack},
+   clip{tc.clip}, holder{std::move(tc.holder)} {}
+#endif
+
 TrackClip::~TrackClip()
 {
 

src/Snap.h

@@ -34,7 +34,8 @@ public:
    TrackClip(Track *t, WaveClip *c);
 
 #ifndef __AUDACITY_OLD_STD__
-   TrackClip(TrackClip&&) = default;
+   // TrackClip(TrackClip&&) = default; is not supported by vs2013/5 so explicit version needed
+   TrackClip(TrackClip&&);
 #endif
 
    ~TrackClip();