Fixed assignment bug in local scope

[kochelmonster]

Fixed the following bugs and avoids to emit the wrong "var" keyword.

def count_100(index):
for j in range(100):
index = index + 1
return index

Generated wrong to:

export var count_100 = function (index) {
for (var j = 0; j < 100; j++) {
var index = index + 1; // var is wrong
}
return index;
};

---

def count_101(index):
idx = index
for j in range(101):
idx = idx + 1
return idx

Generated wrong to:

export var count_101 = function (index) {
var idx = index;
for (var j = 0; j < 101; j++) {
var idx = idx + 1; // var is wrong
}
return idx;
};