Extend tests on `--help' and `--version' options.

Extend tests on `--help' and `--version' options.

* tests/help.test: Create a new empty directory and chdir into
it, rather than removing already present files.  Run the aclocal
and automake wrapper scripts directly, instead of relying on
$AUTOMAKE and $ACLOCAL.  Be sure to correctly match literal dots
in aclocal's and automake's stderr.  Add a trailing `:' command.
* tests/help2.test: New test, checking that options `--help' and
`--version' works in directories with broken `configure.in'.
* tests/help3.test: New test, checking that options `--help' and
`--version' take precedence on the other options.
* tests/help4.test: New test, checking that the first among the
`--help' and `--version' options to be specified on the command
line wins.
* tests/Makefile.am (TESTS): Updated.