CVS Autoconf fails on libltdl configure.in

[Bob Friesenhahn]

When the development version of Autoconf is used to generate a
configure script from CVS libltdl's configure.in this error occurs.

configure.in:36: error: m4_require: circular dependency of AC_LTDL_SYMBOL_USCORE
configure.in:36: AC_LTDL_SYMBOL_USCORE is required by...
./aclocal.m4:3382: AC_LTDL_DLSYM_USCORE is expanded from...
./aclocal.m4:3318: AC_LTDL_SYMBOL_USCORE is expanded from...
configure.in:36: AC_LTDL_SYMBOL_USCORE is required by...
./aclocal.m4:3142: AC_LIB_LTDL is expanded from...
configure.in:36: the top level

The end result is that an empty configure script is generated.  These
actions should be taken:

o Libltdl's configure.in should be fixed so that it is compatible with
  both released and development Autoconf.

o Autoconf should either preserve an existing configure script, or
  should leave no configure script at all after an error.  Empty
  configure scripts have a nasty habit of accidentally getting into
  distributions.

Bob