Fix warning re S24 not trivially copyable by removing copy constructor.

RtAudio.h

@@ -690,7 +690,6 @@ class S24 {
     return *this;
   }
 
-  S24( const S24& v ) { *this = v; }
   S24( const double& d ) { *this = (int) d; }
   S24( const float& f ) { *this = (int) f; }
   S24( const signed short& s ) { *this = (int) s; }