The Finder provides information about how to contact entities within a
system of XORP processes.  For purposes of flexibility and
compatibility, it is desireable to be able to map one XRL into
another, or into a series of XRL's.  As a simple example of
motivation, envisage a situation where a developer wants to trace when
a particular xrl is invoked without any recompilation.  By remapping
the XRL in question to a logging XRL and followed by the original XRL,
this can be achieved with no compilation.

* Syntax for mapping

The remapping might be communicated to the finder with:

finder://fea/interface_enable?running:int=$val {
	# Call another XRL
	finder://logger/record_xrl_call?name:txt="fea/interface_enable"
	# Call original XRL with arguments provided
	finder://fea/interface_enable?running:int=$val 
}

This example re-maps the forwarding engine abstraction (fea)'s method
interface_enable to an alternate routine that logs the xrl invocation
and then calls the original interface_enable method.  The dollar
syntax allows for storage and subsitution of values, here the xrlatom
named "running" and type "int" has it's value propagated.

We can do specialization overloading too, for instance if we only
wanted to overrider interface_enable when the value of running was 1,
we could write:

finder://fea/interface_enable?running:int=1 {
	# Call another XRL
	finder://logger/record_xrl_call?name:txt="fea/interface_enable"
	# Call original XRL with arguments provided
	finder://fea/interface_enable?running:int=1 
}