This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
All cross reference labels start with name of the file that contains
them. A label for the top section level is simply the name of the
file (omitting the .sgml). Other references within the file append a
colon and onother name. For example, the label on the mailing list
section in the file eresources.sgml is eresources:mail. This gives
each file its own cross reference namespace.
