clean-up some library and linkage problems

the object VTable is typically emitted when the compiler
encounters the first non-static non-inline function of
the class or a derived class.

Sometimes this happens within the wrong library and so
the compiler needs a nudge to emit those infrastructure functions.
But in most cases this works out of the box and need no further
magic incanctations, which might have a downside.
Especially because also a non-inline dtor does incur a call overhead,
whereas an inline dtor can be trivially elided.

src/lib/time/timecode.cpp

@@ -48,9 +48,6 @@ namespace lib {
 namespace time {
   
   
-  TCode::~TCode()   { }  // emit VTable here....
-  
-  
   namespace format {  /* ================= Timecode implementation details ======== */ 
     
     LUMIERA_ERROR_DEFINE (INVALID_TIMECODE, "timecode format error, illegal value encountered");

src/lib/time/timecode.hpp

@@ -52,7 +52,7 @@ namespace time {
     {
       
     public:
-      virtual ~TCode();
+      virtual ~TCode() { }
       
       operator string()  const { return show(); }
       string describe()  const { return string(tcID()); }

src/proc/engine/engine-service.cpp

@@ -181,8 +181,6 @@ namespace engine{
   /* ===== Quality-of-Service ===== */
   
   
-  EngineService::Quality::~Quality() { } // emit vtables here...
-  
   enum CalcType {
     PLAYBACK,
     RENDER,

src/proc/engine/engine-service.hpp

@@ -121,7 +121,7 @@ namespace engine{
       class Quality
         {
           public:
-            virtual ~Quality();  ///< this is an Interface
+            virtual ~Quality() { };  ///< this is an Interface
         };