Tuple-Like For Each Iteration

I suggest this syntax to allow foreach loops to operate on more than one collection:
```
For Each (aItem := 0, bItem := 0) in (A, B)
C.Add(aItem + bItem)
Next
```

Note that I am using the `:= ` syntax to set the default value to be used when the loop exceeds the length of one of the collections. If this part is omitted, VB will use the default value of the collection type.
The syntax is very close to tuples, so if should be familiar to us.