libtoolize: aux scripts go in ltdl dir when parent has no configure.

libtoolize: aux scripts go in ltdl dir when parent has no configure.

When using libtoolize to install subproject libltdl into a
parent project that does not use autotools, set the default
directory for auxiliary scripts inside libltdl rather than
littering the parent project with files it doesn't use.
* libtoolize.m4sh (func_require_ac_aux_dir): In verbose mode,
report results like other require_ funcs.
(func_require_aux_dir): Put subproject auxiliary files into ltdl
directory where libltdl/configure will be able to find
`install-sh' and others.

Signed-off-by: Gary V. Vaughan <gary@gnu.org>