Implement global eval

Possible patch from August 08 (it needs revision :D) https://gist.github.com/024e53e62714b9d1219f

Yeah. Looks a little too magical to me : )

• Need to ditch arguments.callee
• arguments.callee.lastReturn = undefined; is redundant
• need to break (script = document.createElement('script')).type = 'text/javascript'; apart
• some values are returned, while others aren't (e.g. 'var x=1; x;'.eval()). Maybe we shouldn't shoot ourselves in the foot by trying to parse string and return value?
• I see document.write, but what happens when document is served as xml?
• document.write inserts script with id which is kind of an invalid html. Can we avoid that?

If the code executes in an iframe won't that defeat the purpose of a global eval because it wont be able to access the properties of the primary window without doing something like parent.blah ?