Broken debugging of JavaScript

[Martin Entlicher]

Hi,

I thought that there is some problem on my side with stepping again. But 
no, this changeset:
https://lafo.ssw.uni-linz.ac.at/hg/graal-js/rev/2dabbd7aec99
effectively removed debugging of JavaScript.

installInstrumenter() method, which is vital for JavaScript debugging 
was moved from JavaScriptLanguage class to JSContext class. This would 
be fine, if it would be called from somewhere. But the call at 
JavaScriptLanguage was removed. :-(

The only single call to installInstrumenter() method is in RunScript, 
but only Shell uses RunScript. The call must be put somewhere before any 
parsing of JavaScript occurs, regardless of where is it parsed from.

Thank you,
Martin