Add optional second parameter to password() function. It can be used to force password()
to return fixed values. 


mysql-test/r/func_crypt.result:
  New test results
mysql-test/t/func_crypt.test:
  new tests
sql/item_strfunc.cc:
  Add optional second argument to password() function
sql/item_strfunc.h:
  New method
sql/sql_yacc.yy:
  Handling of password with 2 arguments