addition to the fix for bug #12177(error log file isn't closed)

libmysqld/lib_sql.cc:
  we should set errorlog_file=0 to make consequent mysql_server_init work
  properly

libmysqld/lib_sql.cc

@@ -628,7 +628,10 @@ void STDCALL mysql_server_end()
   copy_arguments_ptr=0;
   clean_up(0);
   if (errorlog_file)
+  {
     fclose(errorlog_file);
+    errorlog_file=0;
+  }
   /* If library called my_init(), free memory allocated by it */
   if (!org_my_init_done)
     my_end(0);