ofz#3927 ensure same sort order cross platforms

annoyingly was getting different order on oss-fuzz vs normal case
making things hard to reproduce

Change-Id: Ie50a546946b2dfa89bc3af1b4a04a88217c1a668
Reviewed-on: https://gerrit.libreoffice.org/44212Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

sw/source/filter/ww8/ww8scan.cxx

@@ -2701,7 +2701,7 @@ WW8PLCFx_Fc_FKP::WW8Fkp::WW8Fkp(const WW8Fib& rFib, SvStream* pSt,
     maEntries.emplace_back(Get_Long(pStart));
 
     //we expect them sorted, but it appears possible for them to arrive unsorted
-    std::sort(maEntries.begin(), maEntries.end());
+    std::stable_sort(maEntries.begin(), maEntries.end());
 
     mnIdx = 0;