add new tests, new functions

sql-bench/crash-me.sh:
  Add tests:
  
  - If double double quotes are allowed in identifiers. 
  - Rollback rolls back meta data
  - NULL sort and NULL sort perserve. 
  - remove one check of "serial".   
  - (Column,Table,Named constraints) new test to crash me if the check syntax is 
    only supported by the parser, but not done for real.
  - For all ..USER tests, (like current_user), add an extra test if
    ...USER() is supported.                                   
  - Add tests for constants TRUE and FALSE                     
  - Add test of LIMIT # OFFSET (PostgreSQL syntax) 
  - tests of a lot of new functions