[2.4] export balance_dirty

Hello!

We seem to need balance_dirty to be exported now with latest reiserfs patches (so that reiserfs can be built as module). Please apply (against latest 2.4 bk tree).

Thank you.

Bye,
Oleg

===== fs/buffer.c 1.82 vs edited =====

@@ -1026,6 +1026,7 @@
 		write_some_buffers(NODEV);
 	}
 }
+EXPORT_SYMBOL(balance_dirty);
 
 inline void __mark_dirty(struct buffer_head *bh)
 {