More Refactoring to support QVs in database

QV.[ch] and DB.[ch] now need to be compiled with every module as core
support.  DB.[ch] contains routines to support QV access from the
database by applications.  No impact on the top-level module routines,
except for undexqv where the interface to Uncompress_Next_QVentry
changed a bit to support in-core delivery of a QV entry.