[haddock @ 2003-11-05 17:16:04 by simonmar]

Support for generating a single unified index for several packages.

  --use-index=URL  turns off normal index generation, causes Index
 		   links to point to URL.

  --gen-index      generates an combined index from the specified
                   interfaces.

Currently doesn't work exactly right, because the interfaces don't
contain the iface_reexported info.  I'll need to fix that up.