L::DepMap: Remove "soft" unlink'ing of nodes

Signed-off-by: Niels Thykier <niels@thykier.net>
L::DepMap: Rename "map" field to "pending"

Reverse-engineering of L::DepMap suggests that the field "map" seem to
be the set of pending nodes.  Furthermore, it seems that the actual
value associated with members in this set is ignored, so just set it
to 1.

Signed-off-by: Niels Thykier <niels@thykier.net>
L::DepMap: The selected field is a set

The value of keys in the 'selected' field is not used, so it is only
used as a set.  Therefore, set the values to 1 rather than
$complex_data_structure.

Signed-off-by: Niels Thykier <niels@thykier.net>