* NEWS: Updated.

* NEWS: Updated.
* doc/libtool.texi (Libltdl interface): Document new entry
points.
* libltdl/ltdl.c (lt_dladderror): New function to add a user
defined error message to the tables used by lt_dlerror().
(lt_dlseterror):  New function to allow setting of last_error by
user modules.
(ltdl_error_strings): New preprocessor generated table of internal
error diagnostic strings.
(user_error_strings): New internal list of registered user error
diagnostic strings.
(throughout!): Use error messages from ltdl_error_strings.
* libltdl/ltdl.h (ltdl_error_table): New macro to tabulate
internal diagnostic error strings alongside enum keys.