Use a more straightforward hash function

...instead of assembling a OUString and calling OUString::hashCode.  It appears
that these hash values are only used in std::unordered_map instantiations, not
used as part of a stable file format.

Change-Id: Ie3f78b2cc9e162ac9777c7e5f4164a12bc9a62a4

lotuswordpro/source/filter/lwpobjid.hxx

@@ -150,16 +150,8 @@ inline void LwpObjectID::SetHigh(sal_uInt16 nh)
 }
 inline size_t LwpObjectID::HashCode() const
 {
-    OUString str;
-    if(m_nIndex)
-    {
-        str = OUString(m_nIndex) + OUString(m_nHigh);
-    }
-    else
-    {
-        str = OUString(m_nLow) + OUString(m_nHigh);
-    }
-    return str.hashCode();
+    return static_cast<size_t>(
+        (m_nIndex == 0 ? 23 * m_nLow : 27 * m_nIndex) + 29 * m_nHigh);
 }
 
 #endif