Fix for #712 with Serg's suggestions

myisam/mi_locking.c:
  Here we use F_EXTRA_LCK
myisam/myisamchk.c:
  lines of "locking - emulation" replaced with mi_lock_database call
myisam/myisamdef.h:
  no need for MI_TEMPORARY_TABLE
sql/ha_myisam.cc:
  We use F_WRLCK instead MI_TEMPORARY_TABLE

myisam/mi_locking.c

@@ -39,7 +39,7 @@ int mi_lock_database(MI_INFO *info, int lock_type)
   if (share->options & HA_OPTION_READ_ONLY_DATA ||
       info->lock_type == lock_type)
     DBUG_RETURN(0);
-  if (lock_type == MI_TEMPORARY_TABLE)
+  if (lock_type == F_EXTRA_LCK)
   {
     ++share->w_locks;
     ++share->tot_locks;

myisam/myisamchk.c

@@ -878,10 +878,7 @@ static int myisamchk(MI_CHECK *param, my_string filename)
       param->error_printed=0;
       goto end2;
     }
-    share->w_locks++;				/* Mark for writeinfo */
-    share->tot_locks++;
-    info->lock_type= F_EXTRA_LCK;		/* Simulate as locked */
-    info->tmp_lock_type=lock_type;
+    mi_lock_database(info, F_EXTRA_LCK);
     datafile=info->dfile;
 
     if (param->testflag & (T_REP_ANY | T_SORT_RECORDS | T_SORT_INDEX))
@@ -1057,8 +1054,7 @@ static int myisamchk(MI_CHECK *param, my_string filename)
     VOID(lock_file(param, share->kfile,0L,F_UNLCK,"indexfile",filename));
     info->update&= ~HA_STATE_CHANGED;
   }
-  share->w_locks--;
-  share->tot_locks--;
+  mi_lock_database(info, F_UNLCK);
 end2:
   if (mi_close(info))
   {

myisam/myisamdef.h

@@ -101,7 +101,6 @@ typedef struct st_mi_state_info
 #define MI_COLUMNDEF_SIZE	(2*3+1)
 #define MI_BASE_INFO_SIZE	(5*8 + 8*4 + 4 + 4*2 + 16)
 #define MI_INDEX_BLOCK_MARGIN	16	/* Safety margin for .MYI tables */
-#define MI_TEMPORARY_TABLE      ((1 & ~F_RDLCK) | (2 & ~F_WRLCK) | (4 & ~F_UNLCK))
 
 typedef struct st_mi_base_info
 {

sql/ha_myisam.cc

@@ -560,7 +560,7 @@ int ha_myisam::repair(THD *thd, MI_CHECK &param, bool optimize)
 
   // Don't lock tables if we have used LOCK TABLE
   if (!thd->locked_tables && 
-      mi_lock_database(file, table->tmp_table ? MI_TEMPORARY_TABLE : F_WRLCK))
+      mi_lock_database(file, table->tmp_table ? F_EXTRA_LCK : F_WRLCK))
   {
     mi_check_print_error(&param,ER(ER_CANT_LOCK),my_errno);
     DBUG_RETURN(HA_ADMIN_FAILED);
@@ -1002,7 +1002,7 @@ int ha_myisam::external_lock(THD *thd, int lock_type)
 {
   return mi_lock_database(file, !table->tmp_table ?
 			  lock_type : ((lock_type == F_UNLCK) ?
-				       F_UNLCK : MI_TEMPORARY_TABLE));
+				       F_UNLCK : F_EXTRA_LCK));
 }