For PR automake/414:

For PR automake/414:
Introduce options tar-v7, tar-ustar, and tar-pax to select
tar format.
* doc/automake.texi (Options): Document them.
* lib/Automake/Options.pm (_process_option_list): Process
these new options.
* lib/am/distdir.am (dist-gzip, dist-bzip2, dist-tarZ, dist,
distcheck): Adjust to use am__tar and am__untar.
* m4/tar.m4: New file.
* m4/Makefile.am (dist_m4data_DATA): Add tar.m4.
* m4/init.m4 (AM_INIT_AUTOMAKE): Support the new options
and call _AM_PROG_TAR.
* tests/tar.test, tests/tar2.test, tests/tar3.test: New files.
* tests/Makefile.am (TESTS): Add them.