* fixed bug causing empty count results from count-queries with vacuous date- and/or bibl-sort filters
- example: count(* #asc_date) #by[textClass]
- problem was signed/unsigned comparison of index data (DWORD) with filter bounds (int m_KeyLo.i, m_KeyHi.i)
in Bibliography.cpp CConcXml::FileMatches(), CConcXml::CFreeBiblIndex::FileMatches()