Enable `errexit' shell flag in various tests.

Enable `errexit' shell flag in various tests.

* tests/backsl.test: Enable the `errexit' shell flag, and
related changes.
* tests/backsl2.test: Likewise.
* tests/block.test: Likewise.
* tests/canon2.test: Likewise.
* tests/canon4.test: Likewise.
* tests/comment2.test: Likewise.
* tests/condlib.test: Likewise.
* tests/cond15.test: Likewise, and prefer $FGREP over grep.
* tests/canon3.test: Likewise.  Also, avoid to create an useless
dummy source file.
* tests/acoutpt2.test: Enable the `errexit' shell flag, and some
related changes.  Do some cosmetic improvements in the generated
`configure.in' file.
* tests/cond4.test: Likewise.
* tests/cond14.test: Likewise.
* tests/condinc.test: Likewise.
* tests/cond7.test: Likewise.  Also, remove useless setting of
AUTOMAKE_OPTIONS to `foreign' in the generated Makefile.am.
* tests/ansi.test: Enable the `errexit' shell flag, and related
changes.  Extended, esp. by running autoconf, ./configure and
make, and by looking into the distdir.

Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>