Interface Exposure

Exposed functions needed to attach an AXE simulation to the `xgdb` debugger. 

Debug `printf`s have been removed, and test summary is:

```
Testing Time: 18.59s
********************
Failing Tests (1):
    axe :: SystemCalls/overlays.xc

  Expected Passes    : 74
  Unexpected Failures: 1
```
Could you rename the nodeID parameters to jtagIndex (assuming that's what they represent). Also it would be better if axeGetNodeType returned an enum, as currently it not clear what the return value means looking just at this header.