Coerce to Domain

As suggested, I intend to create a 'CoerceToDomain' node in the
expression tree rather than attempting to apply the create the
constraints tests immediately.

1. Create a new function in the executor to handle domain coercions:
ExecEvalCoerceToDomain()

2. Move coerce_type_constraints to the executor (builds expression tree
of constraints) under the name ExecCoerceTypeConstraints().

3. On initial pass, CoerceToDomain will have a 'raw' expression tree
(simple arg of data to coerce). After passing through
ExecCoerceTypeConstraints a 'cooked' expression tree will contain the
constraint tests. Subsequent tuples will simply use the pre-cooked
tree.

--
Rod Taylor <rbt(at)rbt(dot)ca>

PGP Key: http://www.rbt.ca/rbtpub.asc