Don't immediately release temporary VclPtr returned from Create

...the only reason this didn't cause any problems is that the VclPtr returned
from Create already had an mnRefCnt > 1, because of activity in the PushButton
ctor.

Change-Id: I1066ff0b507b8a1ebff079f7b914235a7396368d

include/vcl/btndlg.hxx

@@ -96,7 +96,7 @@ private:
     Link<>              maClickHdl;
 
     SAL_DLLPRIVATE void             ImplInitButtonDialogData();
-    SAL_DLLPRIVATE PushButton*      ImplCreatePushButton( ButtonDialogFlags nBtnFlags );
+    SAL_DLLPRIVATE VclPtr<PushButton> ImplCreatePushButton( ButtonDialogFlags nBtnFlags );
     SAL_DLLPRIVATE ImplBtnDlgItem*  ImplGetItem( sal_uInt16 nId ) const;
     DECL_DLLPRIVATE_LINK(           ImplClickHdl, PushButton* pBtn );
     SAL_DLLPRIVATE void             ImplPosControls();

vcl/source/window/btndlg.cxx

@@ -73,9 +73,9 @@ void ButtonDialog::dispose()
     Dialog::dispose();
 }
 
-PushButton* ButtonDialog::ImplCreatePushButton( ButtonDialogFlags nBtnFlags )
+VclPtr<PushButton> ButtonDialog::ImplCreatePushButton( ButtonDialogFlags nBtnFlags )
 {
-    PushButton* pBtn;
+    VclPtr<PushButton> pBtn;
     WinBits     nStyle = 0;
 
     if ( nBtnFlags & ButtonDialogFlags::Default )