[support] Next and last menu item

[John Fletcher]

I've got a standard navigation-type menu with my pages in it, and a
requirement to show a kind of "back and forward arrow" on each page in
Drupal 6. The back arrow takes you to the previous page in the menu and the
forward arrow takes you to the next page in the menu, and the title of the
relevant page is printed next to the arrows. Like:
Home <-  |  -> About us

The "previous page" means the previous sibling menu item or if none, parent
item.
The "next page" mean the child menu item or, if none, next sibling item, or
if none, next sibling of parent item.

I had a look around the menu API but can't put my finger on the most
efficient way to do this. Anyone know?

Regards,
Fletch