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.


sql/sql_class.h:
  Replaced last_insert_id with autoinc_value_of_last_inserted_row to be
  consistent with 5.1 code.
sql/sql_insert.cc:
  Revised the AUTO_INCREMENT and mysql_insert_id() handling logic in
  INSERT ... SELECT to be consistent with INSERT behavior, the manual, and
  changes in 5.1 introduced by WL3146:
  
  - mysql_insert_id() now returns the first automatically generated
  AUTO_INCREMENT value that was successfully inserted;
  
  -  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.
tests/mysql_client_test.c:
  Backported the test cases related to INSERT ... SELECT and
  mysql_insert_id() from WL3146 patch to 5.0.