SwHTMLPosFlyFrms: fix STL conversion:

It appears that the operator== for SwPosFlyFrm always returns false,
so cf0e08c6 changed the semantics;
use std::mulitset to fix it.

Change-Id: Ib7a8ebe56e146d21c265e60ad68c6b4a319dfe98

sw/inc/flypos.hxx

@@ -55,7 +55,7 @@ public:
     sal_uInt32 GetOrdNum() const { return nOrdNum; }
 };
 
-class SW_DLLPUBLIC SwPosFlyFrms : public std::set<SwPosFlyFrm*> {};
+class SwPosFlyFrms : public std::multiset<SwPosFlyFrm*> {};
 
 #endif // _FLYPOS_HXX