- Run "SHOW WARNINGS" when mysqltest fails and display all but the
   last warning(since it's the same as "last error") on stderr
 - Fix typo


client/mysqltest.c:
  - Display any warnings produced prior to the error that caused
  mysqltest to die.
  - Fix typo "cur_con" -> "con_slot"
  - Move initialization of the "cur_con" pointer to just before it's
    initialized  so it can be used to check if a connection to mysql
    exist.