When the SQL thread cannot read an event from the relay log

("Event too big" etc), stop this thread instead of going on
with the next event, which would certainly lead to slave's data
corruption.

BitKeeper/etc/logging_ok

@@ -16,6 +16,7 @@ bk@admin.bk
 davida@isil.mysql.com
 gluh@gluh.(none)
 greg@mysql.com
+guilhem@mysql.com
 gweir@work.mysql.com
 heikki@donna.mysql.fi
 heikki@hundin.mysql.fi

sql/log_event.cc

@@ -588,6 +588,15 @@ Log_event* Log_event::read_log_event(IO_CACHE* file, bool old_format)
     sql_print_error("Error in Log_event::read_log_event(): '%s', \
 data_len=%d,event_type=%d",error,data_len,head[EVENT_TYPE_OFFSET]);
     my_free(buf, MYF(MY_ALLOW_ZERO_PTR));
+    /*
+      The SQL slave thread will check if file->error<0 to know
+      if there was an I/O error. Even if there is no "low-level" I/O errors
+      with 'file', any of the high-level above errors is worrying
+      enough to stop the SQL thread now ; as we are skipping the current event,
+      going on with reading and successfully executing other events can
+      only corrupt the slave's databases. So stop.
+    */
+    file->error= -1;
   }
   return res;
 }