* m4/module.c (caller_id): To match libtool-2.0 interface, changed
to ...
(iface_id): ...an lt_dlinterface_id type.
(m4__module_find): New abstraction for lt_dlhandle_fetch. Use
throughout, instead of calling obsolete lt_dlhandle_find directly.
(m4__module_next): Use multiloader-safe lt_dlhandle_iterate. Use
throughout, instead of calling obsolete lt_dlhandle_next.
* m4/m4private.h (m4__module_find): Declare it.
* m4/builtin.c (m4_builtin_find_by_name, m4_builtin_find_by_func):
Use m4__module_next instead of obsolete lt_dlhandle_next.