fix immediate linkage, some other fixes to allow vm/ to compile

fix immediate linkage, some other fixes to allow vm/ to compile

* module/language/scheme/translate.scm (lookup-transformer): Allow for
  undefined variables when doing the transformation -- it's possible that
  they come from a module definition's forward declaration.

* module/system/repl/command.scm (import): Make into legal Scheme, caught
  by the compiler :-)

* module/system/vm/assemble.scm (<vlink-now>): Remove the module field.
  Immediate bindings will now always be relative to the current module.
  Fixes some mess about process-define-module not being defined when
  loading modules, probably because we destructively modified the
  ghil-env.
  (codegen, dump-object!): Don't dump a module name.

* src/vm_loader.c (link-now): Just use scm_lookup.