dbug changes:

1. dbug state is now local to a thread
2. new macros: DBUG_EXPLAIN, DBUG_EXPLAIN_INITIAL,
   DBUG_SET, DBUG_SET_INITIAL, DBUG_EVALUATE, DBUG_EVALUATE_IF
3. macros are do{}while(0) wrapped
4. incremental modifications to the dbug state (e.g. "+d,info:-t")
5. dbug code cleanup, style fixes
6. _db_on_ and DEBUGGER_ON/OFF removed
7. rest of MySQL code fixed because of 3 (missing ;) and 6
8. dbug manual updated
9. server variable @@debug (global and local) to control dbug from SQL!
a. -#T to print timestamps in the log

storage/heap/hp_test2.c

@@ -617,7 +617,6 @@ err:
 static int get_options(int argc,char *argv[])
 {
   char *pos,*progname;
-  DEBUGGER_OFF;
 
   progname= argv[0];
 
@@ -646,7 +645,6 @@ static int get_options(int argc,char *argv[])
       printf("Usage: %s [-?ABIKLsWv] [-m#] [-t#]\n",progname);
       exit(0);
     case '#':
-      DEBUGGER_ON;
       DBUG_PUSH (++pos);
       break;
     }