Modernize, improve and/or fix tests `pluseq*.test. * tests/pluseq5.test: Append to configure.in using cat with an here-doc, not using echo. * tests/pluseq10.test: Make sure that the captured output of `make' command is always displayed. Where possible, use $FGREP instead of grep (this change makes some checks slighty stricter). * tests/pluseq8.test: Enable `errexit' shell flag, with related changes. * tests/pluseq.test: Likewise. Also, do not create useless dummy data files, and use better m4 quoting in generated configure.in. * tests/pluseq2.test: Likewise. Also, append to configure.in using cat with an here-doc, not using echo. * tests/pluseq3.test: Likewise. * tests/pluseq4.test: Likewise. * tests/pluseq6.test: Likewise. * tests/pluseq7.test: Do not create useless dummy source file. * tests/pluseq9.test: Slighty extended w.r.t. the grepping of Automake stderr. Some unrelated cosmetic changes. Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>