Add some handling for other default value types.
Add to AIS.
Add to protobuf.
Expose to IS.
Expose to \d.
Actually call the function.
Add a test.
Allow null here, too.
Missed one.
merge mmcm: Improve support for special functions in column DEFAULT.

https://code.launchpad.net/~mmcm/akiban-server/column-default-function/+merge/161307