Prevent Conflicting Function in Lookup

[DavePearce]

At the moment, there seems to be an expected issue whereby a function defined in the global namespace can "hide" a conflicting source (or target) module within a lookup:

(defun (test) m1.Z)

(module m1)
(defcolumns X Y Z)

(module m2)
(defcolumns A)

(deflookup l1 (m1.X m1.Y) (A (test)))