Changes made in qosrns package API to integrate PERD.

* After creating all the links call
	
	$ns configure-perd-qospf-nodes
  
  to configure qospf agents on nodes

* Whenever available bandwidth on a link changes, LS routing agents
  should be informed by the following call.

	RtModule/QOSPF  perd-bw-changed

  this triggers linkstate updates and new route calculations

* RtModule/QOSPF get-perd-explicit-route dest bw traffic

  traffic type is required so that the particular agent
  returns the explicit route to $dest with $bw available


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Example

an example script is provided in tcl/ex/qospf/perd.tcl

Additional changes made for the perd example.

* change ~ns/adc/adc.cc so that admit-flow procedure can be called from
  tcl

* change ~ns/adc/param-adc.cc so that it binds oresv_rate_ so that it can
  be accessed from tcl.

* change ~ns/src_rtg/sragent.cc so that get-path procedure can be called from
  tcl
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