Fix of UNION code

Added heap_delete_table
Added HA_EXTRA_PREPARE_FOR_DELETE
Added and use my_dup() for faster open of tables.
Removed not working no-mix-table-type


BitKeeper/deleted/.del-=6~33f33b0a159dc5d5:
  Delete: =6
heap/hp_clear.c:
  Cleanup
heap/hp_close.c:
  Added delayed delete
heap/hp_create.c:
  Added heap_delete_table
heap/hp_delete.c:
  cleanup
heap/hp_test2.c:
  Added heap_delete_table
include/heap.h:
  Added heap_delete_table
include/my_base.h:
  Added HA_EXTRA_PREPARE_FOR_DELETE
include/my_sys.h:
  Adde my_dup and set_prealloc_root
isam/extra.c:
  Added HA_EXTRA_PREPARE_FOR_DELETE
myisam/mi_check.c:
  use my_dup
myisam/mi_extra.c:
  use my_dup
myisam/mi_open.c:
  use my_dup
myisam/myisamchk.c:
  use my_dup
myisam/myisamdef.h:
  use my_dup
mysys/Makefile.am:
  my_dup
mysys/hash.c:
  Add hash_replace
mysys/mf_pack.c:
  cleanup
mysys/my_alloc.c:
  Add set_prealloc_root
mysys/my_fstream.c:
  cleanup
mysys/my_lib.c:
  cleanup
mysys/my_seek.c:
  cleanup
sql/ha_heap.cc:
  Uses heap_delete_table()
sql/mysqld.cc:
  Fix SIGHUP usage
  Remove no-mix-table-types
sql/share/czech/errmsg.txt:
  new error message
sql/share/danish/errmsg.txt:
  new error message
sql/share/dutch/errmsg.txt:
  new error message
sql/share/english/errmsg.txt:
  new error message
sql/share/estonian/errmsg.txt:
  new error message
sql/share/french/errmsg.txt:
  new error message
sql/share/german/errmsg.txt:
  new error message
sql/share/greek/errmsg.txt:
  new error message
sql/share/hungarian/errmsg.txt:
  new error message
sql/share/italian/errmsg.txt:
  new error message
sql/share/japanese/errmsg.txt:
  new error message
sql/share/korean/errmsg.txt:
  new error message
sql/share/norwegian-ny/errmsg.txt:
  new error message
sql/share/norwegian/errmsg.txt:
  new error message
sql/share/polish/errmsg.txt:
  new error message
sql/share/portuguese/errmsg.txt:
  new error message
sql/share/romanian/errmsg.txt:
  new error message
sql/share/russian/errmsg.txt:
  new error message
sql/share/slovak/errmsg.txt:
  new error message
sql/share/spanish/errmsg.txt:
  new error message
sql/share/swedish/errmsg.txt:
  new error message
sql/sql_base.cc:
  remove no-mix-table-type
sql/sql_parse.cc:
  Fix UNION code

include/my_base.h

@@ -93,7 +93,8 @@ enum ha_extra_function {
   HA_EXTRA_NO_IGNORE_DUP_KEY,
   HA_EXTRA_DONT_USE_CURSOR_TO_UPDATE,	/* Cursor will not be used for update */
   HA_EXTRA_BULK_INSERT_BEGIN,
-  HA_EXTRA_BULK_INSERT_END
+  HA_EXTRA_BULK_INSERT_END,
+  HA_EXTRA_PREPARE_FOR_DELETE
 };
 
 	/* The following is parameter to ha_panic() */