callsite: add `mmodule` and `anchor` to the callsite objects

This simplify the job of its users since more model information is
available.

Signed-off-by: Jean Privat <jean@pryen.org>
rta: add live_callsites and live_callsites

In a callgraph it is useful to be able to compute the live target of any
callsite

Signed-off-by: Jean Privat <jean@pryen.org>
metrics/rta: add callsite_info to display things

Signed-off-by: Jean Privat <jean@pryen.org>
tests: update sav/nitmetrics_args1.res for RTA-callsite info

Signed-off-by: Jean Privat <jean@pryen.org>
Merge: Callgraph

Quick patches so that RTA can give two new pieces of information.

1. what are the live CallSites? `RTA::live_callsites`
2. for each live CallSite, what are the live targets (MMethodDef) `RTA::live_targets`

Pull-Request: #369
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>