SmViewShell: pImpl must outlive aGraphic member

...as at least during CppunitTest_starmath_qa_cppunit, during ~SmViewShell,
aGraphic's code calls back into SmViewShell's code calls into pImpl:

 SmViewShell::IsInlineEditEnabled() const starmath/source/view.cxx:2057:12
 SmGraphicWindow::IsInlineEditEnabled() const starmath/source/view.cxx:227:12
 SmGraphicWindow::CaretBlinkStop() starmath/source/view.cxx:297:10
 SmGraphicWindow::~SmGraphicWindow() starmath/source/view.cxx:126:5
 SmViewShell::~SmViewShell() starmath/source/view.cxx:1976:1
 [...]

This is somewhat symmetric to 0e263d61 "order
pImpl before aGraphic because aGraphic deferences pImpl in ctor."

Change-Id: I97494bebaf5747205a690e6d65fd05ba8fb61cab

starmath/inc/view.hxx

@@ -19,6 +19,10 @@
 #ifndef INCLUDED_STARMATH_INC_VIEW_HXX
 #define INCLUDED_STARMATH_INC_VIEW_HXX
 
+#include <sal/config.h>
+
+#include <memory>
+
 #include <sfx2/dockwin.hxx>
 #include <sfx2/viewsh.hxx>
 #include <svtools/scrwin.hxx>
@@ -224,7 +228,7 @@ class SmViewShell: public SfxViewShell
     // for handling the PasteClipboardState
     friend class SmClipboardChangeListener;
 
-    SmViewShell_Impl*   pImpl;
+    std::unique_ptr<SmViewShell_Impl> pImpl;
 
     SmGraphicWindow     aGraphic;
     SmGraphicController aGraphicController;

starmath/source/view.cxx

@@ -1972,7 +1972,6 @@ SmViewShell::~SmViewShell()
     SmEditWindow *pEditWin = GetEditWindow();
     if (pEditWin)
         pEditWin->DeleteEditView( *this );
-    delete pImpl;
 }
 
 void SmViewShell::Deactivate( bool bIsMDIActivate )