Modernize, improve and extend tests `suffix*.test'. * tests/suffix3.test: Enable `errexit' shell flag, and related changes. * tests/suffix4.test: Likewise. * tests/suffix6.test: Likewise, and do not create a useless dummy source file. * tests/suffix7.test: Likewise. * tests/suffix5.test: Enable `errexit' shell flag, and related changes. Make grepping of Makefile.in slighty stricter. * tests/suffix.test: Enable `errexit' shell flag, and related changes. Also, do not redirect grep output to /dev/null, as this might unmotivatedly hide useful information. * tests/suffix2.test: Move setting of `errexit' shell flag earlier in the script (just after inclusion of ./defs). Use a more idiomatic way to count text occurrences in Makefile.in with grep. Do not create useless dummy source files. * tests/suffix10.test: Ensure verbose printing of captured make stdout. Minor cosmetic changes. * tests/suffix8.test: Likewise. Also, drop useless call to the env(1) utility, and make grepping of make output stricter by using $FGREP rather than plain grep. * tests/suffix11.test: Likewise. * tests/suffix12.test: Likewise. * tests/suffix9.test: Prefet cat + here-doc over echo to append to the `configure.in' stub. Cosmetic changes. * tests/suffix13.test: Cosmetic spacing change. Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>