hi.
rebase because of commit: 8dd7c7cd0a2605d5301266a6b67a569d6a305106
also did minor enhancement.
v4-0001 add function: ExecPrepareExprSafe and ExecInitExprSafe.
v4-0002 add function: DomainHaveVolatileConstraints
v4-0003 tests and apply fast default for domain with constraints.
v4-0003 table with empty rows aligned with master behavior.
also will do table rewrite if the new column is domain with volatile
check constraints,
so less surprising behavior.