vcl: cleanup shared SalYieldMutex from GtkYieldMutex.

Change-Id: I6ace72606ba666322c045d28bea713443c0fc45f

vcl/inc/unx/gtk/gtkinst.hxx

@@ -41,10 +41,7 @@ class GtkYieldMutex : public SalYieldMutex
     std::list<sal_uLong> aYieldStack;
 
 public:
-                        GtkYieldMutex();
-    virtual void        acquire() SAL_OVERRIDE;
-    virtual void        release() SAL_OVERRIDE;
-
+         GtkYieldMutex() {}
     void ThreadsEnter();
     void ThreadsLeave();
 };

vcl/unx/gtk/app/gtkinst.cxx

@@ -276,20 +276,6 @@ SalPrinter* GtkInstance::CreatePrinter( SalInfoPrinter* pInfoPrinter )
 #endif
 }
 
-GtkYieldMutex::GtkYieldMutex()
-{
-}
-
-void GtkYieldMutex::acquire()
-{
-    SalYieldMutex::acquire();
-}
-
-void GtkYieldMutex::release()
-{
-    SalYieldMutex::release();
-}
-
 /*
  * These methods always occur in pairs
  * A ThreadsEnter is followed by a ThreadsLeave