Apple Clang 4.2 caught private members that aren't used in a class
with no friends. Since this code is in a tool, there's no binary
compatibility requirement.

databaseinfo.h:71:13: error: private field 'driver' is not used [-Werror,-Wunused-private-field]
quoter.h:86:10: error: private field 'validRegExp' is not used [-Werror,-Wunused-private-field]
qmlvisitor.h:123:11: error: private field 'tree' is not used [-Werror,-Wunused-private-field]

Change-Id: Iba9995f28ddef983c9ffc1dc551f042539252704
Reviewed-by: Alan Alpert <aalpert@blackberry.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>