Fix funargs problem in Select

The following code:
a : { x : Continue  y : 3 }
i : 1
z : For i : a Select i

Yields:
z : [ 1, 3 ]

Which is rather unexpected. It should produce:
z : [ 3 ]

This change fixes the downward funargs problem introduced by Continue in
For expressions.

Change-Id: I1eac79b186f3876ad90657cce646525985ef290e
Add placeholder for math

Change-Id: Ic1c4aa783b72f2a279574a57807c41f24d9b49e5