djvm loses bookmarks on merges with -create

[Bill Yikes]

Merging multiple djvu files should not be a lossy operation, apart from metadata that only has 1 slot (e.g. author, title, etc). The bookmarks (aka outline) is lost, not merged:

$ djvused -e 'print-outline' file-a.djvu

(bookmarks
 ("foo"
  "#1" ) )

$ djvused -e 'print-outline' file-b.djvu

(bookmarks
 ("bar"
  "#1" ) )

$ djvm -c mergetest.djvu file-a.djvu file-b.djvu

$ djvused -e 'print-outline' mergetest.djvu

(no output)

This data loss is also undocumented. While it wouldn't be necessary to document obvious unavoidable data loss such as doc-wide fields of author and title, the loss of bookmarks is due to an incomplete implementation. And it's unexpected. So this should either be fixed, or the man page should be updated perhaps with a BUGS section warning users of the data loss.