Tree-IL->GLIL: Fix primitive-ref reification bug

* module/language/tree-il/compile-glil.scm (flatten-lambda-case): Fix a
  bug whereby a primitive that is present in the compilation module but
  not at runtime was getting compiled as a toplevel-ref.  This was
  causing current-module to fail to resolve in R6RS modules.

module/language/tree-il/compile-glil.scm

@@ -595,8 +595,7 @@
       
       ((<primitive-ref> src name)
        (cond
-        ((eq? (module-variable (fluid-ref *comp-module*) name)
-              (module-variable the-root-module name))
+        ((eq? (fluid-ref *comp-module*) the-root-module)
          (case context
            ((tail push vals)
             (emit-code src (make-glil-toplevel 'ref name))))