Zexts/Sexts should be included in type constraints.

[2over12]

Currently we ignore sign extend and zero extended copies and not emitting type constraints, we should infer from this behavior that the target is integral and match up the portion extended in the constraint. This issue is backlogged until the solver is implemented.

[2over12]

This is partially fixed in f915967 by assuming that any truncated or extended operation is the weakest integer type.