Add a test that shows that 'make' silently ignores unknown fields

[masak]

When using make on some declared template, leaving field names out is fine, and initializes them to nil.

Language::Bel 0.63 -- msys.
> (tem foo x nil y nil)
((x lit clo nil nil nil) (y lit clo nil nil nil))
> (make foo)
(lit tab (x) (y))

However, using a field name which was not part of the tem declaration means that these are silently dropped.

> (make foo x 1 y 2 z 3)
(lit tab (x . 1) (y . 2))

Add a test to that effect.