r7276: - moved static tdb function ltdb_dn_fold() into common/ so that it can be

r7276: - moved static tdb function ltdb_dn_fold() into common/ so that it can be
  called from multiple backends.  (ldb_sqlite3 needs it too.)  Added parameter
  for a callback function that determines whether an attribute needs case
  folding.
- begin to prepare for sqlite3 in build process
- work-in-progress updates, on ldb_sqlite3
(This used to be commit a80bced0b96ffb655559a43cf7f4d7a34deb5a7d)