Initial implementation.
* added a new capabilities flag CLIENT_CAN_HANDLE_EXPIRED_PASSWORDS
* Added a new server option (and a read only global variable)
disconnect-on-expired-password. Defailt is on. When off it will cause
old clients to get a connection against an expired password account and
get an error for every query that they try to execute that's not 
SET PASSWORD.
* server will check for expired passwords at login and will refuse the 
login if the client didn't set CLIENT_CAN_HANDLE_EXPIRED_PASSWORDS in 
the client hello packet and if the disconnect_on_expired_password 
server side option is set. A detailed error 
(ER_MUST_CHANGE_PASSWORD) will be sent in this case.
* server always sets CLIENT_CAN_HANDLE_EXPIRED_PASSWORDS in
the server hello packet. libmysql never checks for it.
* new mysql_options() option MYSQL_OPT_CAN_HANDLE_EXPIRED_PASSWORDS
to set the CLIENT_CAN_HANDLE_EXPIRED_PASSWORDS flag.
* mysql binary sets MYSQL_OPT_CAN_HANDLE_EXPIRED_PASSWORDS
   if run in interactive mode
* mysqladmin sets MYSQL_OPT_CAN_HANDLE_EXPIRED_PASSWORDS
   if the first command is 'password' or 'old_password'
* mysqltest sets MYSQL_OPT_CAN_HANDLE_EXPIRED_PASSWORDS
* test cases added (both mtr tests and some C test code)
* existing test case results updated to reflect the new server command
line option.
 * fixed the linux compilation problems and test failures