Fix IntegerTest for sqlalchemy-firebird
Fix IntegerTest for sqlalchemy-firebird

Recent cleanup of test_types.py introduced a
regression for sqlalchemy-firebird (and possibly
other external dialects). With this change,
`test_huge_int` now passes for
sqlalchemy-firebird.

Change-Id: Ieeb4b33ec5985f2e2bf6832d1cdef294f85407a0

graingert/sqlalchemy,monetate/sqlalchemy,graingert/sqlalchemy,j5int/sqlalchemy,zzzeek/sqlalchemy,j5int/sqlalchemy,sqlalchemy/sqlalchemy,monetate/sqlalchemy