contrib/wix/defines.wxi

workingctx: overload bookmarks() to return parents' bookmarks

This implements workingctx.bookmarks() parallel to workingctx.tags(),
overloading the implementation from changectx.

<Include>

  <?if $(var.Platform) = "x64" ?>
    <?define IsX64 = yes ?>
  <?else?>
    <?define IsX64 = no ?>
  <?endif?>

</Include>