custom-add-loads: looking for clues

[Mike Kupfer]

I'm trying to understand the (XEmacs) custom-add-loads function, as well
as the custom-load.el file that gets generated for each package as part
of the XEmacs package build.  Can someone give me some clues or point me
at some documentation?

The reason I ask is that with MH-E 7, the generated custom-load.el
contains 

    (autoload 'custom-add-loads "cus-load")
    
    (custom-add-loads 'mh-identity '("mh-customize"))
    (custom-add-loads 'mh-speed-faces '("mh-customize"))
    (custom-add-loads 'mh-index-faces '("mh-customize"))
    (custom-add-loads 'mail '("mh-customize"))
    (custom-add-loads 'mh-alias '("mh-customize"))
    (custom-add-loads 'mh-speed '("mh-customize"))
    ...

The custom-load.el that gets generated for MH-E 8.0.3 just has the
autoload--there are no calls to custom-add-loads.  Is there some tag
that needs to be present in the source file for the custom-add-loads
call to be generated?

There *is* an mh-cus-load.el in the MH-E 8.0.3 tarball (i.e., from
upstream) that has

    (put 'mh-hooks 'custom-loads '("mh-e"))
    (put 'mh-sending-mail 'custom-loads '("mh-e"))
    (put 'mh-sequences 'custom-loads '("mh-e"))
    (put 'mh-junk 'custom-loads '("mh-e"))
    (put 'mh-thread 'custom-loads '("mh-e"))
    (put 'mh-search 'custom-loads '("mh-e"))
    ...

but I can't tell if it's specific to GNU Emacs.  Anyone know?

thanks,
mike