* libltdl/ltdl.m4: that no longer exists.
* configure.in (ACINCLUDE_M4_LIST): Removed libltdl/acinclude.m4.
* Makefile.am (aclocal_macros): Added ltdl.m4.
(libltdl/acinclude.m4): Concatenate libtool.m4 and ltdl.m4.
* bootstrap: Likewise.
* libltdl/Makefile.am (ACLOCAL): Remove the definition. Relying
upon -I may lead to duplicates.
* doc/libtool.texi: Suggest appending ltdl.m4 to acinclude.m4.
* libtoolize.in: Check AC_LIB_LTDL version number in aclocal.m4.
