基于NS2(ns 2.1b8)的qos补丁

Overview of changes in qosrns-0.2-pre1 1. qosrns is implemented as a seperate module, so it can coexist with linkstate routing 2. qosrns uses RtModule interface, thus making it easy to use it with other routing modules 3. qosrns now supports on demand route computation. it is changed by setting