Truffle/Instrumentation:  add TODO comment to Visualizer interface
Truffle/Source:  use a synchronized hash table
fixed match type test
added support to get the generated Node class represented by a NodeClass instance
Truffle: added support for Runtime#getCallTargets()
fix compilation issue; after a method is compiled (but not yet installed), it still needs to call the already compiled children.
reverted matcher to use Class keys instead of NodeClass keys