Fix SfxItemSet pretty printer after some uniqueptr conversions

just whyyyyyyy are you people doing this, why do you gratuitously
break things others rely upon for productivity?!?? I don't give
a F about uniqueptrs, all I want is to be able to print this bloody
SfxItemSet. It's frustrating AF

Change-Id: I0b6110c1806c31a3c098fb9dc73883047191c7f9
Reviewed-on: https://gerrit.libreoffice.org/52362Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>

solenv/gdb/libreoffice/svl.py

@@ -40,7 +40,7 @@ class ItemSetPrinter(object):
         for (whichfrom, whichto) in whichranges:
             size += whichto - whichfrom + 1
             whichids += [which for which in range(whichfrom, whichto+1)]
-        return self._iterator(self.value['m_pItems'], size, whichids)
+        return self._iterator(self.value['m_pItems']['_M_t']['_M_t']['_M_head_impl'], size, whichids)
 
     class _iterator(six.Iterator):