insert ... select.

The 5.0 manual page for mysql_insert_id() does not mention anything
about INSERT ... SELECT, though its current behavior is incosistent
with what the manual says about the plain INSERT.

Fixed by changing the AUTO_INCREMENT and mysql_insert_id() handling
logic in INSERT ... SELECT to be consistent with the INSERT behavior,
the manual, and the changes in 5.1 introduced by WL3146:


- mysql_insert_id() now returns the first automatically generated
AUTO_INCREMENT value that was successfully inserted by INSERT ... SELECT

-  if an INSERT ... SELECT statement is executed, and no automatically
generated value is successfully inserted, mysql_insert_id() now returns
the ID of the last inserted row.