- Added a workaround for SQLAlchemy issue #3023 (fixed in 0.9.5) where
a column that's part of an explicit PrimaryKeyConstraint would not
have its "nullable" flag set to False, thus producing a false
autogenerate.  Also added a related correction to MySQL which will
correct for MySQL's implicit server default of '0' when a NULL integer
column is turned into a primary key column. fixes #199