Generates SQL from Perl datastructures. This is a subclass of SQL::Abstract,
fully compatible with the parent class, but it handles a few additional SQL
constructs, and provides a different API with named parameters instead of
positional parameters, so that various SQL fragments are more easily
identified.

This module was designed for the specific needs of DBIx::DataModel, but is
published as a standalone distribution, because it may possibly be useful for
other needs.
