Bookmarks: Fix update after move

Bookmarks: Fix update after move

do_move_bookmark was only updating the selection in the bookmarks manager
window in which the Move button was pressed. Now all windows are updated.

This patch also prevents a crash when the first item that was displayed
in a box was the last child of a folder and was being moved (the comment
removed in this patch was incorrect in assuming that bm->box->next must
be valid because it neglected to account for non-root children).

This change required that I move the definition of struct
hierbox_dialog_list_item from src/bfu/hierbox.c to src/bfu/hierbox.h.

Thanks to Kalle Olavi Niemitalo for finding both the update problem
and the crash.

[ Backported from commit 6f98f5fd96c8ede06a24a314af95a12cb9b9eb91 in
  ELinks 0.12.GIT.  --KON ]