fix callback routine thread lock issue

[RaptorX]

When making calls for devtools domains from an event callback function chrome.ahk enters an infinite loop because of a thread lock issue

[G33kDude]

I'm not sure if I can merge this one just yet, as it fails to appropriately handle user callbacks when those callbacks are the strings of function names, or already bound functions. I have some thoughts on how that could be resolved, though. It also breaks the functionality of callback functions modifying the result of synchronous calls, but given that actually using that feature would have been a bizarre thing to do I'm ok with breaking it.

I'll probably also strip the commented-out code before merging, since it's no longer needed and if we ever need to refer back we can look at the change history with git blame or similar.