libtool: remove redundant unsubstituted shell var defaults.

libtool: remove redundant unsubstituted shell var defaults.

* Makefile.am (libltdl/config/ltmain.sh): Boilerplate code from
libltdl/config/general.m4 sets some default shell variables
designed to be substituted by `$(configure_edit)'.  Actually,
`libtool' uses the language tag values for those variables, and
`ltmain.m4sh' is not passed through `$(configure_edit)', so they
are just noise.  Edit them out at bootstrap time.

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