tdf#93284 vcl: fix VirtualDevice leaks in the WMF filter

We attempted to have 8884 VirtualDevices in parallel. This number is now
12 after fixing the leaks.

The original bugdoc has 135 images, 76 is enough to make Writer on
Windows crash. The minimized document has the same WMF data for all the
images, but still duplicated inside the ZIP container, so we trigger the
resource limit, but the document is still just 99K.

Change-Id: I4c6b3853eaf688302323daf67ff7b62dd64fc412
(cherry picked from commit 047ebb1d)
Reviewed-on: https://gerrit.libreoffice.org/17825Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

vcl/source/filter/wmf/winmtf.cxx

@@ -236,7 +236,7 @@ WinMtfFontStyle::WinMtfFontStyle( LOGFONTW& rFont )
     {
         // #i117968# VirtualDevice is not thread safe, but filter is used in multithreading
         SolarMutexGuard aGuard;
-        VclPtrInstance< VirtualDevice > pVDev;
+        ScopedVclPtrInstance< VirtualDevice > pVDev;
         // converting the cell height into a font height
         aFont.SetSize( aFontSize );
         pVDev->SetFont( aFont );
@@ -1451,7 +1451,7 @@ void WinMtfOutput::DrawText( Point& rPosition, OUString& rText, long* pDXArry, b
     {
         // #i117968# VirtualDevice is not thread safe, but filter is used in multithreading
         SolarMutexGuard aGuard;
-        VclPtrInstance< VirtualDevice > pVDev;
+        ScopedVclPtrInstance< VirtualDevice > pVDev;
         sal_Int32 nTextWidth;
         pVDev->SetMapMode( MapMode( MAP_100TH_MM ) );
         pVDev->SetFont( maFont );
@@ -1499,7 +1499,7 @@ void WinMtfOutput::DrawText( Point& rPosition, OUString& rText, long* pDXArry, b
         {
             // #i117968# VirtualDevice is not thread safe, but filter is used in multithreading
             SolarMutexGuard aGuard;
-            VclPtrInstance< VirtualDevice > pVDev;
+            ScopedVclPtrInstance< VirtualDevice > pVDev;
             pDX = new long[ rText.getLength() ];
             pVDev->SetMapMode( MAP_100TH_MM );
             pVDev->SetFont( maLatestFont );