Fixed that automatic killing of delayed insert thread (in flush, alter table etc) will not abort auto-repair of MyISAM table.

Give more information when finding an error in a MyISAM table.
When killing system thread, use KILL_SYSTEM_THREAD instead of KILL_CONNECTION to make it easier to ignore the signal in sensitive context (like auto-repair)
Added new kill level: KILL_SERVER that will in the future to be used to signal killed by shutdown.
Add more warnings about killed connections when warning level > 3

include/myisamchk.h:
  Added counting of printed info/notes
mysys/mf_iocache.c:
  Remove duplicate assignment
sql/handler.cc:
  Added test of KILL_SERVER
sql/log.cc:
  Ignore new 'kill' error ER_NEW_ABORTING_CONNECTION when requesting query error code.
sql/mysqld.cc:
  Add more warnings for killed connections when warning level > 3
sql/scheduler.cc:
  Added checks for new kill signals
sql/slave.cc:
  Ignore new kill signal ER_NEW_ABORTING_CONNECTION
sql/sp_head.cc:
  Fixed assignment to bool
  Added testing of new kill signals
sql/sql_base.cc:
  Use KILL_SYSTEM_THREAD to auto-kill system threads
sql/sql_class.cc:
  Add more warnings for killed connections when warning level > 3
  thd_killed() now ignores KILL_BAD_DATA and THD::KILL_SYSTEM_THREAD as these should not abort sensitive operations.
sql/sql_class.h:
  Added KILL_SYSTEM_THREAD and KILL_SERVER
sql/sql_connect.cc:
  Added handling of KILL_SERVER
sql/sql_insert.cc:
  Use KILL_SYSTEM_THREAD to auto-kill system threads
  Added handling of KILL_SERVER
sql/sql_parse.cc:
  Add more warnings for killed connections when warning level > 3
  Added checking that thd->abort_on_warning is reset at end of query.
sql/sql_show.cc:
  Update condition for when a query is 'killed'
storage/myisam/ha_myisam.cc:
  Added counting of info/notes printed
storage/myisam/mi_check.c:
  Always print an an error if we find data errors when checking/repairing a MyISAM table.
  When a repair was killed, don't retry repair.
  Added assert if sort_get_next_record() returned an error without an error message.
  Removed nonsence check "if (sort_param->read_cache.error < 0)" in repair.
storage/myisam/myisamchk.c:
  Added counting of notes printed
storage/pbxt/src/thread_xt.cc:
  Better error message.

sql/sql_class.h

@@ -1838,7 +1838,9 @@ public:
     NOT_KILLED=0,
     KILL_BAD_DATA=1,
     KILL_CONNECTION=ER_SERVER_SHUTDOWN,
+    KILL_SYSTEM_THREAD=ER_NEW_ABORTING_CONNECTION, /* Kill connection nicely */
     KILL_QUERY=ER_QUERY_INTERRUPTED,
+    KILL_SERVER,	 /* Placeholder for shortdown */
     KILLED_NO_VALUE      /* means neither of the states */
   };
   killed_state volatile killed;