First version of new authentification procedure: now authentification is one-stage (instead of two-stage in 4.1)

For now following tasks have been done:
- PASSWORD() function was rewritten. PASSWORD() now returns SHA1
  hash_stage2; for new passwords user.password contains '*'hash_stage2; sql_yacc.yy also fixed; 

- password.c: new functions were implemented, old rolled back to 4.0 state

- server code was rewritten to use new authorization algorithm (check_user(), change
  user, and other stuff in sql/sql_parse.cc)

- client code was rewritten to use new authorization algorithm
  (mysql_real_connect, myslq_authenticate in sql-common/client.c)

- now server barks on 45-byte-length 4.1.0 passwords and refuses 4.1.0-style
  authentification. Users with 4.1.0 passwords are blocked (sql/sql_acl.cc)

- mysqladmin.c was fixed to work correctly with new passwords

Tests for 4.0-4.1.1, 4.1.1-4.1.1 (with or without db/password) logons was performed;
mysqladmin also was tested. Additional check are nevertheless necessary.

sql/sql_class.cc

@@ -139,6 +139,7 @@ THD::THD():user_time(0), is_fatal_error(0),
   set_query_id=1;
   db_access=NO_ACCESS;
   version=refresh_version;			// For boot
+  *scramble= *scramble_323= '\0';
 
   init();
   /* Initialize sub structures */