Add NOT NULL as keyword (fixes issue18).
Add NOT NULL as keyword (fixes issue18).

adamgreenhall/sqlparse,AndiDog/sqlparse,Yelp/sqlparse,andialbrecht/sqlparse,Yelp/sqlparse,zhongdai/sqlparse,benekastah/sqlparse,payne/sqlparse,payne/sqlparse,adamgreenhall/sqlparse,zhongdai/sqlparse,actsasgeek/sqlparse,tailhook/sqlparse,MariaPet/sqlparse,actsasgeek/sqlparse,tailhook/sqlparse,vmuriart/sqlparse,payne/sqlparse,zhongdai/sqlparse,AndiDog/sqlparse,adamgreenhall/sqlparse,actsasgeek/sqlparse,AndiDog/sqlparse,MariaPet/sqlparse,Yelp/sqlparse,tailhook/sqlparse