MARPLOT BINARY LAYER FILE FORMAT: NNX (name index) files

THis file may not always exist for a given layer on a given map.  When it does,
it applies to all layers whose layer names match the prefix of the NNX file,
possibly including an extension in parentheses.  For instance, if there is a
NNX file "ROADS.NNX", this file contains an index into both the "ROADS" and
"ROADS (MAJOR)" layers on the map.  The .NNX file is a list of pairs.  Each
pair contains a long, which is an offset into an OBJ file, and a small integer
n, where n determines which of the layers with the same name (modulo          
parenthetical extensions) the object belongs to.  n ranges from 1 to the number
of layers with the given name.  n indexes the layers in alphabetical order.
For instance, in the case of the roads example, if n = 1 the object is on the
"ROADS" layer, and if n = 2, the object is on the "ROADS (MAJOR)" layer, since
it is aplabetically second.

Here is the format:

offset (long)
layer n (byte)
< repeat for number of objects in union of files with the given name >

The file is ordered according to the following sort expression:

    name + prefix + place name + CFCC