Feature: support comment on CREATE statements

[greizgh]

Right now parsing a CREATE TABLE statement will fail:

• if there are comments on some field
• if there is a comment on the table itself

Exemple:

CREATE TABLE withcomments (
...
field VARCHAR(100) COMMENT 'some field',
...
) COMMENT='table description';

It would be nice to support those. I'm not yet really familiar with nom, but I would gladly help on this feature.