- When converting ModuleNames to Modules for use in the the module
  initialisation code, look them up in the IfaceTable(s) instead of
  calling findModule again.  They are guaranteed to be in either
  the HomeIfaceTable or the PackageIfaceTable after the renamer,
  so this saves some trips to the filesystem.  Also, move this
  code earlier in the compilation cycle to avoid holding on to the
  renamed syntax for too long (not sure if this makes a difference or
  not, but it definitely looked space-leakish before).

- remove Util.unJust, it is a duplicate of Maybes.expectJust