Avoid harmless unused variable warning in the ownerdrw sample.

MSVC8 gives

.\ownerdrw.cpp(96) : warning C4189: 'pFrame' : local variable is initialized
but not referenced

so just don't define this variable to avoid the warning.

samples/ownerdrw/ownerdrw.cpp

@@ -92,9 +92,7 @@ bool OwnerDrawnApp::OnInit(void)
     if ( !wxApp::OnInit() )
         return false;
 
-    OwnerDrawnFrame *pFrame
-        = new OwnerDrawnFrame(NULL, wxT("wxWidgets Ownerdraw Sample"),
-                              50, 50, 450, 340);
+    new OwnerDrawnFrame(NULL, "wxWidgets Ownerdraw Sample", 50, 50, 450, 340);
 
     return true;
 }