Testsuite: ensure verbose printing of captured stderr.

Testsuite: ensure verbose printing of captured stderr.

* tests/acloca18.test: Print captured stderr before either failing
or grepping it.  Be sure to send captured stderr to stderr, not to
stdout.
* tests/ansi3b.test: Likewise.
* tests/cond39.test: Likewise.
* tests/configure.test: Likewise.
* tests/missing3.test: Likewise.
* tests/missing6.test: Likewise.
* tests/output-order.test: Likewise.
* tests/pr300-ltlib.test: Likewise.
* tests/python6.test: Likewise.
* tests/python7.test: Likewise.
* tests/python8.test: Likewise.
* tests/python9.test: Likewise.
* tests/subobj.test: Likewise.
* tests/vars3.test: Likewise.
* tests/missing4.test: Likewise, and fix a call to grep not to use
the `-c' flag.
* tests/ansi3.test: Likewise, and rely on the `configure.in' stub
created by `./defs', rather than writing one from scratch.

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