It's a secret tool we'll use later on.

Add IterativeInterp, a modified version of Interp that can be stepped through execution, preventing infinite loops.

Just using the readme to explain what this fork is.

Forgot about this little thinger...

Should quiet things down a bit

`assign()`  (usually triggered by `EBinop("="...`) was not searching through the stack to find local vars outside of the immediate block's scope. It now does so. 

Also identified a few areas that used the same search method and merged them into a single inlined function, `find_local(id:String):Dynamic`. 

There are only minor differences between `find_local` and `resolve`, and they could potentially be merged with some adjustments to `assign`, `increment`, etc.

Two codeblocks ending consecutively with no expression in between 
eg
```
if(foo){
    if(bar){
        trace('hello');
    }
    //no expression here would trigger the bug
}
```
Would crash the script. The fetch phase will now, on encountering the end of a block, continue bubbling up through stack frames until it either finds one that will continue or returns a value and ends the script.

Now fully compatible with -DhscriptPos. Internally-generated expressions simply show "Internal" source and zero for all line/position telemetry. 

Fixed a bug where pushing a new frame to the stack wasn't updating locals.

Tools.exprify(e:Expr/ExprDef):Expr is basically the equivalent of Tools.mk for runtime-generated (ie, has no position in source hscript) exprs. It allows hscript.IterativeInterp to be compatible with -DhscriptPos.

Added support for for loop syntax; for loops exist in their own stack frame and can be interrupted as with other loops.

Array declarations now support function calls as members.

Improved PosInfo for internal expressions.

`continue` now works as expected in while, dowhile, and for loops.