Fix parsing foreign key constraints with multiple dots.
Fix parsing foreign key constraints with multiple dots.

moonrabbit/alembic,sqlalchemy/alembic,chishaku/alembic,Frozenball/alembic,ideadevice/alembic,6si/alembic,ideadevice/alembic,6si/alembic,Frozenball/alembic,zzzeek/alembic,ImaginationForPeople/alembic,fsys/alembic,moonrabbit/alembic,fsys/alembic,graingert/alembic