samba/NSSWITCH interaction in fbsd 10 vs fbsd 8

When I try use the libnss_winbind.so  that is generated by samba 3.6 I 
get the following message:

  NSSWITCH(nss_load_module): winbind, Undefined symbol 
"nss_module_register".

First I have to change its' name to nss_winbins.so.1 however because 
that is what nsswitch is looking for....
(BTW where is that documented??)

then it finds it but fails as mentioned above.

This same samba source generates good nss files in 8.0 but under 10 it 
fails.. Literally it's the same sources just checked out into a 
different build system. (10 vs 8).

Has there been a change in the API for the nss modules? where it he 
API for nsswitch files documented?

Julian