Second correction to the TH fix of Oct 26, involving thFAKE

Original message
  1) A bug in the renaming of [d| brackets |]. The problem was
  that when we renamed the bracket we messed up the name cache, because
  the module was still that of the parent module. Now we set a fake
  module before renaming it.

This commit fixes the typecheker problem in a different way,
in tcLookupGlobal.